JP2003306009A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing rigidity difference and dimensional difference of a cord cut end part and preventing air infiltration to the cord cut end part. <P>SOLUTION: A side part of at least a piece of carcass ply 5 which is a parallel arrangement of a cut cord is wound up around a bead core 4 so that the carcass ply 5 is toroidally arranged, and at least one of belt layers 6, 7 and 8 arranged in parallel of the cut cord is provided on an outer peripheral side of a crown part of the carcass ply 5. A protective layer 10 for covering the cord cut end is provided adjacently to the cord cut end of the belt layer 7 while having a small space from it. The bending rigidity of a fiber member constituting the protective layer 10 is 1/10 or less with respect to the bending rigidity of a cord of a main cord reinforced layer covered by the protective layer 10. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides one or more carcass plies in which cutting cords are arranged in parallel, the side parts of which are wound around a bead core and arranged in a toroidal shape. On the outer peripheral side,
This is also a pneumatic tire with more than one belt layer in which cutting cords are arranged in parallel, and effectively reduces the dimensional and rigidity steps at the cord cutting ends such as carcass ply cords and belt layer cords. In addition, the present invention relates to a pneumatic tire having a significantly improved durability by preventing the occurrence of separation or the like at the cord end.

[0002]

2. Description of the Related Art For example, a steel cord having a large bending rigidity is often used as a cord forming a belt layer as a constituent member of a pneumatic tire, and the cut end surface of the cord is usually the inner or outer surface of the belt layer. Since it is at a right angle to the belt layer, a large difference in rigidity due to the action of various external forces occurs between the portion where the belt layer is disposed and the portion where the belt layer is not disposed, and a dimensional step corresponding to the diameter of the steel cord is generated. It will be. Therefore, in order to fill such a difference, it has been generally practiced conventionally to devise the shape and physical properties of the rubber disposed adjacent to the cut end of the cord.
However, steel cord has much higher flexural rigidity than rubber, and it is practically impossible to sufficiently reduce the rigidity difference due to rubber.Therefore, shaping during raw tire molding and vulcanization mold In molding it, the deformation of the steel cord as the belt layer cord cannot be sufficiently followed by the deformation of the raw tire and the like, and therefore,
There is a possibility that air may enter the portion adjacent to the cut end of the belt layer cord, and such air is likely to be an initial nucleus of a crack, which may cause a factor of belt separation.

And, these things were almost the same at the cut end of the carcass ply cord.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. The object of the present invention is to provide a rigid step due to a belt layer cord, a carcass ply cord and the like. Another object of the present invention is to provide a pneumatic tire which can effectively alleviate or absorb a dimensional step and always sufficiently prevent air from entering the cord cut end.

[0005]

In order to achieve the above object, the pneumatic tire of the present invention has one or more carcass plies in which cutting cords are arranged in parallel, and the side portions thereof are rewound around a bead core. Carcass ply as a main cord reinforcing layer. Further, a protective layer is provided adjacent to the cord cutting end of at least one of the belt layers with a narrow interval so as to cover the cord cutting end, and the protective layer covers the bending rigidity of the fiber member constituting the protective layer. The bending rigidity of the cord of the main cord reinforcing layer is set to 1/10 or less.

[0006] Here, in addition to the above, in the pneumatic tire having a bead portion or one or more kinds of sub cord reinforcing layers in which cut cords are arranged in parallel from the bead portion to the sidewall portion, , A protective layer is provided in the vicinity of the cord cutting end of at least one type of sub cord reinforcing layer so as to cover the cord cutting end at a small interval, and protects the bending rigidity of the fiber member that constitutes this protective layer. 1/10 of the bending rigidity of the cord of the sub cord reinforcing layer covered by the layer
The following is preferable.

According to this, the rigidity of the portion adjacent to the cord cutting end is increased by the protective layer covering the cord cutting end, and by extension, the fiber member forming the cord, and the thickness of the protective layer is used to absorb the dimensional step. Various steps can be effectively mitigated by contributing to this, and therefore, the protective layer against the shaping during shaping of the green tire and the deformation of the belt layer or the like during the shaping in the vulcanization process. Through the deformation of the belt layer cord, etc. to which it adheres, can be advantageously deformed, and by itself embedding the dimensional step of the cord cutting end, effectively entering air into the cord cutting end. Can be prevented. Moreover, here, the flexural rigidity of the fiber member constituting the protective layer is set to 1/10 or less of the flexural rigidity of the cord covered by the fiber member so that the protective layer is deformed due to rubber flow or the like, so that It is possible to deform the cord more smoothly along the line, and it is possible to more effectively prevent air from entering the cut end of the cord. If the bending rigidity ratio exceeds 1/10, the effect of deforming the protective layer along the cord cut end becomes insufficient, and the effect of preventing air from entering the cord cut end decreases.

By the way, as a mode of covering the cord cut ends of the main and sub cord reinforcing layers with the protective layer, the protective layer is provided from the portion near the cord cut end to the portion near the cord cut end from the cord cut end. When projecting outward in the tire width direction or in the radial direction and when wrapping around the cut end surface of the cord and folding it back, the former further has the cord cut end from at least one of the inner peripheral side and the outer peripheral side of the cord reinforcing layer. There are cases where it is covered and cases where it is covered from at least one of the inner side and the outer side of the cord reinforcing layer in the tire width direction. The number of reinforcing layers here can be appropriately selected as required, but when the cord diameter is large or the cord rigidity is particularly high, a dimensional step and a rigidity step are provided by using a plurality of protective layers. It is advantageous to alleviate

In the above description, preferably,
The protective layer is made of biaxial fabric. According to this, the cord cutting end can be restrained from two directions by the fiber member of the biaxial woven fabric, and the protective layer is more effective to the cord cutting end face based on the force from the two directions acting on the protection layer. Therefore, the rigidity and the dimensional step can be alleviated more advantageously.

Further, preferably, the diameter of the fiber member constituting the protective layer is 0.5 times or less than the diameter of the cord constituting the cord reinforcing layer covered by the protective layer. In this case, the degree of freedom of deformation of the fibrous member can be increased, so that the protective layer can be more smoothly clinged to the cord cut surface. When the diameter of the fiber member constituting the protective layer is larger than 0.5 times the diameter of the coat constituting the cord reinforcing layer covered by the protective layer, the stress intensity factor at the end of the protective layer is much smaller than that of the cord reinforcing layer. Since it does not become small, there is a slight risk of separation from the edge of the protective layer.

The fiber member constituting the protective layer may be a monofilament cord made of an organic fiber material such as nylon, polyethylene terephthalate or aromatic polyamide, or a monofilament cord made of a metal fiber material such as steel. For example, the increase in weight can be advantageously suppressed, and the latter can greatly enhance the ability to support input of compressive force, tensile force, shearing force, and the like.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a widthwise sectional view showing an embodiment of the present invention with respect to a half portion of a tire, in which 1 is a tread portion and 2 is a side extending inward in a radial direction continuously from a side portion of the tread portion 1. Reference numeral 3 denotes a wall portion, and reference numeral 3 denotes a bead portion which is continuous with the inner peripheral side of the sidewall portion 2 in the radial direction.

Here, at least one carcass ply 5 is arranged to extend toroidally between the bead cores 4 arranged in the respective bead parts 3 to reinforce the respective parts 1, 2 and 3, and the carcass ply 5 is provided. The side portions of the are wound around the bead core 4 radially outward. Further, on the outer peripheral side of the crown portion of such a carcass ply 5, three belt layers 6, 7 and 8 in the figure are arranged with the belt layer cords crossing each other. A wire chafer 9 may be arranged in the bead portion 3 along the winding portion of the carcass ply 5.

Here, the carcass ply 5 and the belt layers 6, 7, 8 as the main cord reinforcing layer and the wire chafer 9 as the sub cord reinforcing layer are all cut at both ends in parallel with each other. Placed in
It becomes a parallel arrangement structure of cutting code.

As shown in this figure, a protective layer 10 preferably made of a biaxial woven fabric is arranged on the inner peripheral side of the intermediate belt layer 7 located between the three belt layers 6, 7, 8. At the same time, the protective layer 10 is positioned in the vicinity of the cord cutting end 7a of the intermediate belt layer 7 so as to be adjacent to the cord cutting end 7a with a small gap therebetween, so that the cord cutting end 7a is protected by the protective layer 10. Cover from the inner circumference side.
More specifically, with respect to the cord cutting end 7a, the protection layer 10 is projected from the portion near the cord cutting end 7a to the outside in the tire width direction from the cord cutting end 7a along the portion near the cutting end. Realize the cover.

FIG. 2 is a schematic view showing the extending mode of the protective layer 10 in this case as seen from the inner peripheral side of the tire. In the figure, the black dots indicate the cord strands and the meshed portions indicate the protective layer. 10 is shown. The overlap width between the belt layer 7 and the protective layer 10 can be appropriately selected as required.

By the way, such covering with the protective layer 10 can be carried out from at least one of the inner peripheral side and the outer peripheral side of the intermediate belt layer 7, and this can be applied to the other belt layers 6 and 8 as well. It is also the same. Figure 3 shows an example
FIG. 5 is a cross-sectional view of a main part of a tread portion showing a case where a cord cut end 7a of an intermediate belt layer 7 is covered from both inner peripheral side and outer peripheral side. Here, the protective layer 1 disposed on both sides of the inner and outer peripheries of the intermediate belt layer 7 in the vicinity of the cord cutting end 7a.
Both 0 and 11 extend along the portion near the cut end and are arranged so as to project outward from the cord cut end in the tire width direction. FIG. 4 is a schematic diagram showing an extending mode of the protective layers 10 and 11 shown in FIG. 3 as viewed from the tire inner circumference side. In this case, the dimensional step and the rigidity step can be alleviated more advantageously than in the case where only the protective layer 10 is provided. In addition, in the place shown in the drawing, each of the protective layers 10 and 11 is a single layer,
It is also possible to make at least one of them two or more layers, and when the protective layer is a plurality of layers, a dimensional difference may occur when the cord diameter of the cord reinforcing layer is large or the cord rigidity is particularly high. Also, it is advantageous in alleviating the rigidity step, and the movement of the rubber near the cord cutting end can be further suppressed, and as a result, the effect of suppressing the occurrence of cracks near the cord reinforcing layer end is improved.

FIG. 5 is a cross-sectional view of an essential part in the width direction of the tread portion showing another embodiment, in which the protective layer 12 disposed near the cord cutting end 7a of the intermediate belt layer 7 is cut into cords. In the figure, it is folded back in a channel shape so as to wrap the end face. Here, too, the protective layer 12 can be made up of two or more layers.

FIG. 6 is a cross-sectional view in the width direction of the bead portion 3 showing still another embodiment, showing an arrangement mode of the protective layer with respect to the cord cut end at the winding end of the carcass ply 5. In this figure, the protective layer 13 is arranged in the vicinity of the winding end of the carcass ply 5 along with it.
Is a folded and extended form that wraps around the cord cutting end face.

As with the disposition of the protective layer for the cord cut end of the belt layer, the protective layer is provided at the inner side and the outer side in the tire width direction in the vicinity of the cord cut end also at the rewind end. It is also possible to extend along the part and to extend so as to project radially outward from the cord cutting end. 7 (a),
(B) is a schematic diagram showing the relative relationship between the rewound portion and the protective layer in this case as seen from the inside in the tire width direction,
FIG. 7 (a) shows a mode in which the protective layer is arranged inside the winding portion of the carcass ply in the width direction so as to be adjacent to the cord cutting end 5a with a small gap therebetween.
(B) shows a mode in which the protective layer is disposed adjacent to both inner and outer sides in the tire width direction of the roll-back portion with a narrow space therebetween. Also with these protective layers,
It is possible to bring about the same effect as that of the above-mentioned protective layer provided for the belt layer.

FIG. 8 is a cross-sectional view of the bead portion in the width direction, in which the protective layer 14 is folded back by wrapping the cord cut end at the radially outer end of the wire chafer 9 as an example of the sub-cord reinforcing layer. It is extended in the form. The protective layer for the wire chafer 9 can also be made to project and extend in the tire outer peripheral direction from a portion in the vicinity of the cord cutting end in the same manner as the protective layer at the cord cutting end of the carcass ply. Is arranged on at least one of the inner side and the outer side in the tire width direction with respect to the wire chafer 9. Although the protective layer 14 is shown as a single layer in the figure, it is also possible to have a plurality of layers of two or more layers.

In the above description, the bending rigidity of the fiber members forming the respective protective layers 10 to 14 is set to 1/10 or less of the rigidity of the cord forming the main or sub cord reinforcing layer covered by the fiber members. According to this, of the protective layer,
When deforming due to rubber flow, etc., it can be deformed more smoothly along the cord cutting end face, and the dimensional step and rigidity step can be alleviated more advantageously, and the air entering the cord cutting end is more effective. Can be prevented.

Further, preferably, the protective layers 10 to 14 are formed of a biaxial woven fabric, and more preferably, the diameter of the fiber members constituting the protective layers is set to 0 of the diameter of the cord as an object covered by the fiber members. 5 times or less. According to the former, the cord cutting end can be restrained from two directions by the biaxial woven fiber member, and the protective layer is more effective to the cord cutting end face based on the force from the two directions acting on the protection layer. Further, according to the latter, since it is possible to increase the degree of freedom of deformation of the fibrous member, it is possible to more smoothly cling to the cord cutting surface of the protective layer,
Rigidity and dimensional difference can be alleviated more advantageously, and air can be prevented from entering the cord cut end more effectively.

Further, the fiber member constituting the protective layer is a monofilament cord made of an organic fiber material such as nylon, polyethylene terephthalate or aromatic polyamide, or
It may be a monofilament cord made of a metal fiber material such as steel. According to the former, it is possible to advantageously suppress an increase in weight, and according to the latter, it is possible to greatly enhance the ability to support input of compressive force, tensile force, shearing force, and the like.

Although not shown, the protective layer can also be applied to the so-called hollowed belt layer in which the central portion in the width direction of the belt layer is omitted, as described above.

[0026]

Example 1 A size of 11 / for the purpose of investigating the durability of the portion of the belt layer cord of the tread portion near the cut end.
In 70 R22.5 truck and bus tires,
The steel cord forming each of the three belt layers has a cord diameter of 1.06 mm and a structure of (1 + 6) × 0.34
The number of cords is set to 24/50 mm, the cords of the innermost belt layer rise 20 degrees to the right when the tire is viewed from the front, the cords of the intermediate belt layer rise 20 degrees to the left, and the cords of the outermost belt layer to the right. The carcass ply cord made of steel cord has a cord diameter of 1.00 mm and a structure of (3 + 9 + 15) ×
0.165, the number of cords is 30/50 mm, and the ply cords have a basic structure in which the extending direction of the ply cords is the direction perpendicular to the tire equatorial plane. For each of the comparative example tires 1 to 3, the filling air pressure to the tire was 800 kPa,
The tire was disassembled after running for 48 hours under a constant load condition of a load of 27 kN and a side force of 15 kN at a speed of 60 km / h, and then the length of crack progress along the cord extending direction from the cut end of the belt layer cord was measured. The average value on the circumference was calculated, and index evaluation was performed using the crack length of Comparative Example tire 1 without a protective layer as a control. The results are shown in Table 1.
The smaller the index value in Table 1, the shorter the crack length. Here, as shown in Table 1, the test tire is also made of a material for the protective layer, a driving density, the number and configuration of the layers, an extension angle of the fiber member of the protective layer with respect to the tire circumferential direction, and a fiber member of the protective layer. Five types of example tires and three types of comparative example tires were obtained by combining the ratio of the bending rigidity of the above with the bending rigidity of the cord of the main cord reinforcing layer (bending rigidity ratio in Table 1).

[0027]

[Table 1]

In Table 1, when the example tires and the comparative example tires are compared, all the example tires have shorter crack lengths than the comparative example tires, and the protective layer is provided at the cord cutting end. It can be seen that by setting the bending rigidity of the fiber member to 1/10 or less of the bending rigidity of the cord of the main cord reinforcing layer, an excellent effect of suppressing cracks can be obtained. Comparing Example tires 1 and 2, it can be seen that the protective layer having two layers rather than one layer has a better effect on crack suppression. Further, comparing Example tires 2 and 4, even with the same two-layer arrangement, when the reinforcing layer is arranged so as to wrap around its end face and arranged to be folded back, the crack length is further shortened and an excellent effect on crack suppression is obtained. I know that it will work.

(Example 2) For the purpose of investigating the durability of the portion of the bead portion near the cut end of the carcass ply cord, an example tire 6 and a comparative example tire having the same basic structure as described in example 1 will be described later. For each of 4 to 5, the tire filling air pressure was 800 kPa and the speed was 60 km /
h, with load of 27 kN, running for 100,000 km, then disassembling the tire, measuring the crack length in the cord extending direction near the cut end of the carcass ply cord of the bead rubber, and determining the average value on the circumference. The crack length of Comparative Example tire 4 without the protective layer was calculated and indexed. The results are shown in Table 2. The smaller the index value, the shorter the crack length. Here, the test tires are also in Table 2
As shown in Fig. 3, the material of the protective layer, the driving density, the number and configuration of the layers, the extension angle of the protective layer with respect to the carcass ply cord, the bending rigidity of the fiber member of the protective layer with respect to the bending rigidity of the cord of the main cord reinforcing layer, By combining the ratios (bending rigidity ratios in Table 2), one kind of example tire and two kinds of comparative example tires were obtained.

[0030]

[Table 2]

In Table 2, comparing the example tires with the comparative example tires, the example tires all had shorter crack lengths than the comparative example tires, were covered with a protective layer at the carcass ply cord end, and the fibers of the protective layer were It can be seen that by setting the bending rigidity of the member to 1/10 or less of the bending rigidity of the cord of the main cord reinforcing layer, an excellent effect of preventing the occurrence of cracks can be obtained.

[0032]

As is apparent from the above description, according to the present invention, a cord is provided by disposing a protective layer at the cord cut end of a main cord reinforcing layer such as a carcass ply cord or a belt cord layer. By increasing the rigidity of the part adjacent to the cut end, it is possible to absorb the dimensional step by the thickness of the protective layer. At the same time, the bending rigidity of the fiber member of the protective layer is Since it is 1/10 or less, the protective layer can be deformed more smoothly along the cord cutting end face, so that air is prevented from entering the reinforcing layer cord cutting end during tire production, and thus cracking and development are prevented. However, the durability life of the tire can be significantly improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in a width direction showing an embodiment of the present invention about a half part of a tire.

FIG. 2 is a schematic view illustrating a mode in which a cut end of a belt layer cord is covered with a protective layer.

FIG. 3 is a cross-sectional view of essential parts of a tread portion illustrating an example in which a cut end of a belt layer cord is covered with a protective layer from both inner and outer circumferences.

FIG. 4 is a schematic view illustrating an embodiment in which a cut end of a belt layer cord is covered with a protective layer from both inner and outer circumferences.

FIG. 5 is a cross-sectional view of essential parts of a tread portion illustrating a mode in which a cut end of a belt layer cord is folded back and covered with a protective layer.

FIG. 6 is a cross-sectional view in the width direction of the bead portion, illustrating a mode in which the cut end of the carcass cord is covered with a protective layer.

FIG. 7 is a schematic view illustrating a mode in which a cut end of a carcass cord is covered with a protective layer.

FIG. 8 is a cross-sectional view of a bead portion in the width direction illustrating a mode in which a cord cut end of a wire chafer is covered with a protective layer.

[Explanation of symbols]

1 tread section 2 Side wall part 3 bead part 4 bead core 5 radial carcass 6, 7, 8 belt layers 9 wire chafers 10-14 Protective layer

Claims (7)

[Claims] 1. One or more carcass plies in which cutting cords are arranged in parallel are wound around the bead core and arranged in a toroidal shape, and also on the outer peripheral side of the crown portion of the carcass ply. A pneumatic tire having one or more belt layers in which cut cords are arranged in parallel, and a narrow gap is provided in the vicinity of the cord cut end of at least one of the carcass ply and the belt layer as a main cord reinforcing layer. In addition, a protective layer adjacent to the cut end of the cord is provided,
A pneumatic tire in which the bending rigidity of the fiber member forming the protective layer is set to 1/10 or less of the bending rigidity of the cord of the main cord reinforcing layer covered by the protective layer. 2. A bead portion, or one or more kinds of sub cord reinforcing layers for arranging cut cords in parallel are arranged from the bead portion to the side wall portion, and at least one kind of sub cord reinforcing layer has a cord cut end. A protective layer that covers the cord cut end is provided adjacently at a small interval in the vicinity, and the bending rigidity of the fiber member that constitutes this protective layer is The pneumatic tire according to claim 1, which is 1/10 or less. 3. The protective layer is arranged so as to protrude from the portion near the cord cutting end, along the portion near the cutting end, and outward in the tire width direction or the radial direction from the cord cutting end. The pneumatic tire according to 1 or 2. 4. The pneumatic tire according to claim 1, wherein the protective layer is provided by wrapping around the cord cut end surface and folding it back. 5. The pneumatic tire according to claim 1, wherein the protective layer is formed of a biaxial woven fabric. 6. The diameter of the fiber member forming the protective layer is 0.5 times or less the diameter of the cord forming the main or sub cord reinforcing layer protected by the protective layer.
The pneumatic tire according to any one of 5 above. 7. The pneumatic tire according to claim 1, wherein the fiber member constituting the protective layer is a monofilament cord of organic fiber or metal fiber.