JPH10287103A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freely adjust the rigidity of a side part of a tire, and reduce the used quantity of carcass cord so as to lower the cost by continuously combining the going and returning of carcass cords between a pair of right and left bead cores and the going and returning thereof in side areas in the circumferential direction so as to form a carcass cord layer. SOLUTION: A carcass layer is stretched between a pair of right and left bead parts, and both the ends of the carcass layer are locked with bead cores 3, 3. The carcass layer is formed by making go and return one or plural carcass cords between a pair of right and left bead cores 3, 3 and while making go and return it in side areas. Furthermore, this going and returning of the carcass cords between the bead cores 3, 3 and the going and returning thereof in the side areas are continuously combined in the circumferential direction of a tire for extension. With this structure, rigidity of tire in the circumferential direction is improved, and operating stability and high-speed durability are improved, and productivity is improved. Rigidity of the side part can be adjusted by adjusting height of a folding part 9, and used variable of the carcass cord is reduced so as to lower the cost.

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 a carcass cord is reciprocated between a pair of right and left bead portions to form a carcass layer. More specifically, the present invention improves durability, steering stability and productivity. The present invention relates to a pneumatic tire capable of freely adjusting the rigidity of a side portion and reducing the amount of use of a carcass cord, thereby enabling cost reduction.

[0002]

2. Description of the Related Art Conventionally, when a carcass layer applied to a general pneumatic radial tire is formed, a plurality of previously arranged carcass cords are subjected to a calendering process to rubberize unvulcanized rubber. After cutting the rubberized sheet material in the longitudinal direction to a size slightly longer by the winding height at both ends than the radial length of the carcass layer, these cut pieces are singularized according to the tire size. Alternatively, a carcass material is formed by joining a plurality of pieces so as to have a required circumferential length in the tire circumferential direction.

[0003] The carcass material thus prepared is transferred to a green tire forming process, wound around a forming drum, and then bead cores are fitted to both ends of the outer periphery thereof. A green tire is formed by winding up so as to envelop and further winding side rubber or the like.

However, in the carcass layer formed in this manner, a cut fracture surface of the carcass cord is formed at the wound end of the formed carcass material, and the cut fracture surface is formed on the tire sidewall portion having a large deformation amount. Due to the presence, stress concentration on the cut fracture surface often caused tire failure. In addition, in this carcass structure, there is a problem that a reinforcing layer accompanied by an increase in weight must be added as necessary in order to sufficiently secure the circumferential rigidity of the tire side portion. Further, in order to form such a carcass layer, there are a number of steps such as cutting the sheet material through the above-described calendering step and splicing the cut pieces, and this causes a decrease in productivity. Had become.

On the other hand, various tires have been proposed in which a carcass layer is continuously knitted from one carcass cord to form a carcass structure having no cut fracture surface. For example, Japanese Patent Laying-Open No. 1-110941 discloses that the carcass structure is formed by sequentially passing a carcass cord by a reciprocating motion of a rotating arm between a pair of holding mechanisms arranged in a circle.

However, in the above carcass structure, the carcass cord is continuously reciprocated and knitted between the pair of right and left bead portions, and thus the rigidity of the side portion cannot be adjusted as necessary. The degree of freedom is limited to a small degree, and it is practically impossible to reduce the amount of carcass cord used to reduce the cost.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to improve durability, steering stability and productivity, adjust the rigidity at the side portions, and reduce the amount of carcass cord used to reduce costs. It is to provide a pneumatic tire which enables the following.

[0008]

In order to achieve the above object, a pneumatic tire according to the present invention reciprocates a carcass cord between a pair of left and right bead cores, and includes a left and right bead core and a shoulder portion adjacent to each bead core. And a carcass layer is formed by continuously extending the reciprocation between the bead cores and the reciprocation in the side region while continuously combining them in the tire circumferential direction.

In this manner, the carcass cord is reciprocated between the pair of left and right bead cores and reciprocated to the left and right side regions between the bead core and the shoulder portion. By forming the carcass layer by continuously extending in the direction and forming the carcass layer, since the carcass layer does not have a cut fracture surface, the occurrence of edge separation in the carcass layer is prevented, and the load durability is improved. In addition, since the carcass cords are arranged so as to extend in the tire circumferential direction in the reciprocating folded portion in the side region, the rigidity in the tire circumferential direction can be increased, and the steering stability and high-speed durability can be improved.

Further, as described above, the carcass cord is continuously reciprocated between the pair of right and left bead cores and between the left and right side regions to form the carcass layer. It is not necessary to form a carcass layer through the above step, and the productivity of the tire can be increased. Further, in the carcass structure, the carcass cord is reciprocated in the left and right side regions, and the height of the reciprocating folded portion can be arbitrarily set, so that the rigidity of the side portion can be freely adjusted, and In the lower region of the belt layer where the carcass cord does not receive much tension, it is possible to reduce the amount of use of the carcass cord and reduce the cost.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. 1 to 3 exemplify a pneumatic tire according to an embodiment of the present invention. In the figure, between a pair of left and right bead portions 1 and 1,
The carcass layer 2 is mounted, and both ends in the tire width direction of the carcass layer 2 are locked to the bead core 3. Outside the carcass layer 2 in the tread portion 4, two belt layers 5 are arranged annularly over one circumference of the tire.

As shown in FIGS. 2 and 3, the carcass layer 2 reciprocates one or a plurality of carcass cords 6 between a pair of left and right bead cores 3, 3 and also connects the left and right bead cores 3 with each bead core 3. It is formed by reciprocating to the side area 8 between the adjacent shoulder portions 7 and extending while continuously combining the reciprocation between the bead cores 3 and 3 and the reciprocation of the side area 8 in the tire circumferential direction. I have.

In the drawing, the carcass cord 6 makes one reciprocation in the left and right side regions 8 while making one reciprocation between the bead cores 3. However, the pattern and ratio of this combination are not particularly limited, and can be arbitrarily arranged in the tire circumferential direction. In the present invention, assuming that the number of carcass cords 6 passing through the side region 8 is Z and the number of carcass cords 6 reciprocating between the bead cores 3 is B, 0 <B /
Z <1, more preferably 0.2 <B / Z <0.
The carcass layer 2 may be formed in the range of 6.

On the other hand, the bead lock structure for the carcass cord 6 is not particularly limited.
Various forms can be adopted as shown in FIG. That is, in FIG. 4A, the carcass cord 6 is
Reciprocates in the side region 8 outside the outside. In FIG. 4B, the bead core 3 is inserted so that the carcass cord 6 is spirally wound around the bead core 3. In FIG. 4C, the bead core 3 is inserted into one of a pair of loops formed by the carcass cord 6. In FIG. 4D, the carcass cord 6
Is sandwiched between two bead cores 3. Further, in FIG. 4E, the bead core 3 is sandwiched from inside and outside by a pair of loops formed by the carcass cord 6. In any bead lock structure,
The carcass cords 6 do not contact each other.

As described above, the carcass layer 2 is formed by continuously combining the reciprocation between the bead cores 3 and 3 of the carcass cord 6 and the reciprocation of the side region 8 in the tire circumferential direction, whereby the carcass layer 2 is cut and broken. Has no surface,
It is possible to prevent edge separation in the carcass layer 2 and improve load durability. In addition, since the carcass cords 6 are arranged so as to extend in the tire circumferential direction in the reciprocating folded portion 9 in the side region 8, the rigidity in the tire circumferential direction can be increased, and steering stability and high-speed durability can be improved.

Further, as described above, the carcass cord 6 is continuously reciprocated between the pair of right and left bead cores 3 and 3 and between the left and right side regions 8 to form the carcass layer 2. It is not necessary to form the carcass layer through a complicated and many steps such as steps, and the productivity of the tire can be increased. Therefore, in the present invention, compared to a pneumatic tire having a cut fracture surface in the carcass layer,
Excellent durability, handling stability and productivity.

In the carcass structure, since the height of the reciprocating folded portion 9 in the left and right side regions 8 can be set arbitrarily, the rigidity of the side portion can be freely adjusted. This makes it possible to reduce the amount of use of the carcass cord 6 in the lower region of the belt layer 5 where the tension due to the tire internal pressure is not so much applied to the carcass cord 6, thereby achieving cost reduction.

Therefore, compared to a pneumatic tire knitted by continuously reciprocating the carcass cord between the pair of right and left bead portions without breaks, the degree of freedom in design is increased and the cost can be reduced. In the above-mentioned carcass structure, at least a part of the carcass cords 6 in all the carcass cords reciprocate between the pair of right and left bead cores 3, so that blow molding can be performed at the time of tire molding.

In the present invention, the height H of the reciprocating folded portion 9 in the side region 8 from the inner diameter surface of the bead core 3 is set.
In this case, all the reciprocating folded portions 9 may be the same in the tire circumferential direction, or may be different at random. By making the height H of the reciprocating folded portion 9 different in this way, it is easy to adjust the rigidity of the side portion, and the degree of freedom in design is increased. Further, the height H of the reciprocating folded portion 9 from the inner diameter surface of the bead core 3 is preferably set to 15 mm or more. Thus, the reciprocating turn 9
By setting the height H to 15 mm or more, the rigidity of the side portion can be sufficiently ensured. The upper limit of the height H of the reciprocating folded portion 9 is up to a position corresponding to the edge of the belt layer 5.

[0020]

EXAMPLES Tires 1 and 2 of the present invention, conventional tires and comparative tires having tire sizes of 185 / 60R14 and different carcass structures only as described below were manufactured.

The tire 1 carcass cord of the present invention is reciprocated between a pair of left and right bead cores and reciprocated in left and right side regions between the bead core and the shoulder portion. As shown in FIG. 4 (a), the carcass layer was formed by alternately combining them at a ratio of 1: 1 in the tire circumferential direction, and the height from the bead core of the reciprocating folded portion in the side region was set to 50 mm.

The carcass structure was the same as that of the tire 1 of the present invention except that the height of the reciprocating folded portion in the side region of the tire 2 of the present invention from the bead core was 20 mm.

Conventional tire As shown in FIG. 5, a carcass material having a cut surface of a carcass cord is mounted between a pair of left and right bead portions, and both end portions in the tire width direction of the carcass material are wound around a bead core from the inside to the outside of the tire. By winding up, the winding height of the carcass cord was set to 50 mm.

Comparative tire As shown in FIG. 6, the carcass cord was continuously reciprocated between a pair of left and right bead portions to form a carcass layer.

The test tires were evaluated for productivity, side rigidity, steering stability, load durability, and carcass cord usage by the following test methods, and the results are shown in Table 1.

Productivity: For each test tire, the number of tires produced per unit time was determined, and the result was indicated by an index with the conventional tire being 100. The larger the index value, the higher the productivity.

Side stiffness: The stiffness of each test tire in the direction of the tire rotation axis was measured and expressed as an index with the conventional tire being 100. The circumferential rigidity of the side portion increases as the index value increases.

Driving stability: Each test tire was subjected to an air pressure of 1.9.
The vehicle was mounted on a 1.6-liter domestic passenger car with a displacement of kg / cm ² and a feeling test was performed by a test driver. The evaluation results were indicated by an index with the conventional tire being 100. The larger the index value, the better the steering stability.

Load durability: The load durability was evaluated by a test method according to JIS D4230, and the conventional tire was evaluated as 1
The index is set to 00. The larger the index value, the better the load durability.

Carcass cord usage: For each tire, the carcass cord usage was determined.
The index was set to 0. The smaller the index value, the smaller the amount of carcass cord used.

[0031]

As is apparent from Table 1, the tires 1 and 2 of the present invention are superior in load durability, steering stability and productivity as compared with the conventional tire using a carcass material having a cut fracture surface. Thus, the amount of carcass cord used could be reduced while maintaining the same side rigidity as the conventional tire.

[0033]

As described above, according to the present invention, the carcass cord is reciprocated between the pair of left and right bead cores, and reciprocates in the side regions between the left and right bead cores and the shoulder portions adjacent to the respective bead cores. By forming the carcass layer by continuously combining the reciprocation between the bead cores and the reciprocation of the side regions in the tire circumferential direction to form a carcass layer, compared to a conventional pneumatic tire having a cut fracture surface in the carcass layer. The rigidity of the side portion can be adjusted while improving the durability, steering stability, and productivity, and the amount of carcass cord used can be reduced to reduce costs.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view illustrating a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a carcass layer of the tire of FIG.

FIG. 3 is a plan view showing a carcass layer of the tire of FIG.

FIGS. 4A to 4E are perspective views illustrating a bead lock structure in the tire of FIG. 1;

FIG. 5 is a perspective view showing a bead lock structure of a conventional tire.

FIG. 6 is a perspective view showing a bead lock structure of a comparative tire.

[Description of Signs] 1 Bead portion 2 Carcass layer 3 Bead core 6 Carcass cord 7 Shoulder portion 8 Side area

Claims (3)

[Claims] 1. A carcass cord is reciprocated between a pair of left and right bead cores, and reciprocates in side regions between the left and right bead cores and shoulder portions adjacent to the respective bead cores. A pneumatic tire in which a carcass layer is formed by extending while continuously combining reciprocation in the tire circumferential direction. 2. The pneumatic tire according to claim 1, wherein a height of the reciprocating folded portion in the side region from the bead core is set to a plurality of different sizes. 3. The pneumatic tire according to claim 1, wherein the height of the reciprocating folded portion in the side region from the inner diameter surface of the bead core is 15 mm or more.