JP2010274859A - Pneumatic tire - Google Patents

Abstract

[PROBLEMS] To improve pressure resistance in a pneumatic tire having a bead core formed by winding a plurality of bead wires arranged in parallel in an annular shape.
In a pneumatic tire 1 in which a bead core 3 formed by winding a plurality of bead wires 5 arranged in parallel in a tire width direction on a bead portion 2 in a plurality of stages is arranged. In the cross section in the width direction, the vertical thickness of the bead wire 5 is A (mm), the vertical thickness of the bead core 3 is H (mm), the distance from the tire axis to the outermost position in the tire radial direction of the bead core 3 is B (mm), air H / A ≧ 4 and C + 5 (mm) ≧ B, where C (mm) is the distance from the rim axis of the applicable rim R suitable for the tire 1 to the rim radial outermost position of the rim flange. Try to meet.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire in which a bead core formed by winding a plurality of bead wires arranged in parallel in the tire width direction in a plurality of stages in a ring shape is provided on a bead portion, and in particular, tire safety. It is an object of the present invention to provide a pneumatic tire that can be reduced in weight without deteriorating performance.

  A bead core is embedded in the bead portion of the pneumatic tire in order to moor the carcass made of the carcass ply, and this bead core can be configured by continuously winding one bead wire (for example, see Patent Document 1). A plurality of bead wires arranged in parallel can be wound in an annular shape (see, for example, Patent Document 2), and which configuration is selected can be determined according to the line type of the bead wire.

  By the way, in recent years, efforts to environmental problems have been activated, which is no exception in the tire industry. That is, tires are required to save resources by reducing the weight and reducing materials for the purpose of reducing the fuel consumption of vehicles. In order to meet such a demand, it is effective to reduce the amount of bead wire used in connection with the fact that the bead core is usually formed of a metallic bead wire and the weight ratio is larger than other parts. On the other hand, a certain level of safety as a tire must be ensured.

JP 2005-28944 A JP-A-2005-145082

  In view of such circumstances, a pneumatic tire equipped with a bead core in which a plurality of bead wires arranged in parallel is annularly wound at the stage of repeated research considering the weight reduction of the bead core is continuous with one bead wire. As compared with a pneumatic tire provided with a bead core that is wound in a wound manner, it has been found that pressure resistance performance is lowered when the amount of bead wire used is the same. Since the pressure resistance greatly affects the fit between the tire and the rim, it is important to improve the pressure resistance in order to reduce the amount of bead wire used.

  Therefore, the present invention is based on the knowledge that if the pressure resistance can be improved, the use amount of the bead core can be reduced, and the bead core is formed by winding a plurality of bead wires arranged in parallel in a ring shape. An object of the present invention is to improve the pressure resistance performance of a pneumatic tire equipped with a tire.

The present invention has been made to solve the above problems, and a pneumatic tire according to the present invention includes a pair of bead portions, a pair of sidewall portions extending outward in the tire radial direction from the bead portions, and both sidewalls. A tread portion extending between the portions, and each bead portion is provided with a bead core formed by plurally winding a plurality of bead wires arranged in parallel in the tire width direction in a plurality of stages. In the tire, in the tire width direction cross section, the vertical thickness of the bead wire is A (mm), the vertical thickness of the bead core is H (mm), and the distance from the tire axis to the outermost position in the tire radial direction of the bead core is B (mm) H / A ≧ 4, where C (mm) is the distance from the rim axis of the applicable rim suitable for the pneumatic tire to the rim radial outermost position of the rim flange. C + 5 (mm) ≧ B, it is an its features to satisfy.
As used herein, “vertical thickness of the bead wire” refers to a distance measured along the winding direction of the bead wire in the tire width direction cross section, and “vertical thickness of the bead core” refers to a cross section in the tire width direction. The bead core shall be the distance measured along the bead wire winding direction. “Applicable rim” is a standard determined by an industrial standard effective in the region where the tire is produced or used, for example, “THE TIRE AND RIM ASSOCIATION INC. YEAR BOOK” in the United States, “The European Tire and Rim Technical Organization's STANDARDS MANUAL”. In Japan, this is the rim specified in the “JATMA YEAR BOOK” of the Japan Automobile Tire Association.

  The inventor of the present application diligently studied the problem of a decrease in pressure resistance of a pneumatic tire having a bead core formed by annularly winding a plurality of bead wires arranged in parallel. In a pneumatic tire having a bead core in which bead wires are wound in an annular shape, the bead core breaks from the position where the winding start end of the bead wire exists (see FIG. 4), that is, the position where the number of stacked bead wires changes. In addition, it was found that the pre-breaking location is the inside in the tire width direction (bead toe side). Then, the inventors have found out that the cause is that a rigidity step is generated as a result of a change in the number of laminated bead wires at a position where the winding start end of the bead wire exists.

  Therefore, in the present invention, in the tire width direction cross section, when the vertical thickness of the bead wire is A and the vertical thickness of the bead core is H, H / A ≧ 4. Thereby, the rigidity step at the winding start end position of the bead wire can be made relatively small, and the pressure resistance performance can be improved. On the other hand, when the outermost position in the tire radial direction of the bead core is set higher than the outermost position in the rim radial direction of the rim flange, the bead core that is pressed outward in the tire width direction by the carcass during internal pressure filling cannot be supported by the rim flange ( In the present invention, the distance from the tire axial line to the outermost position in the tire radial direction of the bead core is further set to B (mm), and the applicable rim is adapted to the pneumatic tire. When the distance from the rim axis of the rim to the outermost position in the rim radial direction of the rim flange is C (mm), C + 5 (mm) ≧ B. As a result, the pressure resistance of the tire can be improved efficiently.

  In the pneumatic tire according to the present invention, each bead wire constituting the bead core may be provided with an engaging portion that complements and engages between the bead wires adjacent to each other in the tire width direction. preferable.

  According to the present invention, it is possible to improve the pressure resistance performance in a pneumatic tire having a bead core formed by winding a plurality of bead wires arranged in parallel in an annular shape, thereby easily reducing the weight of the bead core. To be able to plan.

FIG. 1A is a tire width direction sectional view showing a part of a pneumatic tire according to an embodiment of the present invention, and FIG. 1B is an enlarged view of the bead wire of FIG. is there. FIG. 2A is a tire width direction sectional view showing a part of a pneumatic tire according to another embodiment of the present invention, and FIG. 1B is an enlarged view of the bead wire of FIG. Is. FIG. 3 is a cross-sectional view of a bead wire that can be suitably used in the present invention. It is a partial side view of the bead core applied to the conventional pneumatic tire. It is tire width direction sectional drawing which showed a part of pneumatic tire (comparative example 1) as a comparison. It is tire width direction sectional drawing which showed a part of pneumatic tire (comparative example 2) as a comparison. It is tire width direction sectional drawing which showed a part of pneumatic tire (comparative example 3) as a comparison.

  Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1A is a tire width direction sectional view showing a part of a pneumatic tire according to an embodiment of the present invention, and FIG. 1B is an enlarged view of the bead wire of FIG. Is.

  The pneumatic tire 1 shown in FIG. 1 has a tread portion (not shown) that contacts the road surface, a pair of sidewall portions (not shown) that extend inward in the tire radial direction from both sides of the tread portion, A pair of bead portions 2 that are provided on the inner side in the tire radial direction of the sidewall portion and are fitted to the rim R are provided. Inside the pneumatic tire 1, for example, a radial structure carcass 4 extending in a toroidal shape between bead cores 3 embedded in each bead portion 2 to form a skeleton structure of the pneumatic tire 1, and a crown region of the carcass 4 A belt (not shown) for reinforcing the tread portion is disposed on the outer peripheral side of the belt. The carcass 4 is wound back from the inside of the tire 1 around the bead core 3, and both ends thereof are fixed in the bead portion 2.

  The bead core 3 is configured by winding six bead wires 5 arranged in parallel substantially in the tire width direction in an annular manner in six layers along the tire circumferential direction. The cross-sectional shape of the bead wire 5 constituting the bead core 3 is not particularly limited, and may be a rectangle as illustrated, or may be a circle, another polygon, or other irregular closed shape. The adjacent bead wires 5 are in direct contact with each other, that is, no rubber or the like is interposed between the bead wires 5 and 5.

  Conventionally, a bead core 3 formed by annularly winding a plurality of bead wires 5 arranged in parallel has a rigidity step at the position where the winding start end E of the bead wire 5 exists (see FIG. 4). Occasionally, the bead core 3 was easily broken from this vicinity.

  On the other hand, in the pneumatic tire 1 of this embodiment, when the vertical thickness of the bead wire 5 is A and the vertical thickness of the bead core 3 is H in the cross section in the tire width direction, H / A ≧ 4. Thereby, the rigidity level | step difference in the winding start end position of the bead wire 5 can be made relatively small, and pressure | voltage resistant performance can be improved. On the other hand, if the outermost position in the tire radial direction of the bead core 3 is set higher than the outermost position in the rim radial direction of the rim flange, the bead core 3 pressed outward in the tire width direction by the carcass 4 at the time of internal pressure filling can be supported by the rim flange. As a result of the occurrence of a portion that disappears (near the upper end of the bead core 3), the bead core 3 tends to collapse. From the viewpoint of suppressing this, the distance from the tire axis (not shown) to the outermost position in the tire radial direction of the bead core 3 (hereinafter referred to as "bead core 3"). “Bead core top height” is B (mm), the distance from the rim axis (not shown) of the applicable rim R that fits the pneumatic tire 1 to the outermost position in the rim radial direction of the rim flange (hereinafter referred to as “rim”). C + 5 (mm) ≥B, where C (mm) is the flange height). This makes it possible to efficiently improve the pressure resistance of the tire.

  More preferably, when the lateral thickness of the bead wire 5 is a (mm), a ≧ A and the cross-sectional shape of the bead wire 5 is flat. According to this, it becomes possible to more effectively reduce the rigidity step. More preferably, it is preferable that a / A, which is the ratio of the lateral thickness a and the longitudinal thickness A of the bead wire 5, is 1.2 or more. According to this, it is possible to achieve both a reduction in the amount of use of the bead wire 5 and an improvement in the pressure resistance performance of the bead core 3 in a high dimension.

  Next, a pneumatic tire according to another embodiment of the present invention will be exemplified. FIG. 2 is a sectional view in the tire width direction showing a part of a pneumatic tire according to another embodiment of the present invention.

  In the example shown in FIG. 2, each bead wire 5 constituting the bead core 3 is provided with an engagement portion 6 that complements and engages between the bead wires 5 and 5 adjacent in the tire width direction. is there. In this example, in the adjacent bead wires 5, 5, the convex engagement portion 6 of one bead wire 5 and the concave engagement portion 6 of the other bead wire 5 complement each other in shape, and are firmly engaged. It is a configuration that demonstrates the resultant power.

  Thereby, the rotational rigidity of the bead core 3 (the force for suppressing the pull-out of the carcass 4) against the force to rotate the bead core 3 by the carcass 4 at the time of air filling, load application, or change with time. Since it can be remarkably increased, the durability of the bead portion 2 can be improved in addition to the improvement of the pressure resistance performance, and the amount of the bead wire 5 used can be more effectively reduced while ensuring the safety of the tire. it can. The bead wire 5 having the engaging portion 6 is not limited to the one shown in FIG. 2, and as illustrated in FIGS. 3 (a) and 3 (b), the cross-sectional shape is a parallelogram, or a convex portion and a concave portion. The shape can be a point-symmetric arrangement.

  Although the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the claims. For example, the arrangement of the bead wires 5 The number is not limited to six and can be four or seven. Further, the number of stacked layers of the bead wires 5 is not limited to six, and may be five or seven as long as the above formula “C + 5 (mm) ≧ B” is satisfied.

  In the pneumatic tire of tire size 275 / 80R22.5, the pneumatic tires of Examples 1 and 2 in which only the configuration of the bead core was made different, and the pneumatic tires of Comparative Examples 1 to 3 were made as prototypes for comparison. Since the evaluation was made on the property, it will be described below.

  The pneumatic tire of Example 1 has the bead core shown in FIG. 1 in the bead portion, and the bead core has an annular tire diameter in which six bead wires having a rectangular cross-sectional shape are arranged in parallel in the tire width direction. It is constructed by winding up six stages in the direction. Detailed specifications of the pneumatic tire of Example 1 are as shown in Table 1.

  The pneumatic tire of Example 2 has the bead core shown in FIG. 2 in the bead portion, and the cross-sectional shape of the bead wire is substantially arrow-shaped and complementarily complements each other between adjacent bead wires. It has a mating engagement part. Detailed specifications of the pneumatic tire of Example 2 are as shown in Table 1.

  The pneumatic tire of Comparative Example 1 has the bead core shown in FIG. 5 in the bead portion, and the bead core is formed by arranging six bead wires arranged in parallel in the tire width direction in an annular shape in three stages in the tire radial direction. It is constructed by winding up. The cross-sectional shape of the bead wire is substantially arrow-shaped, and has an engaging portion that complements and engages between adjacent bead wires. Detailed specifications of the pneumatic tire of Comparative Example 1 are as shown in Table 1.

  The pneumatic tire of Comparative Example 2 has the bead core shown in FIG. 6 in the bead portion, and the bead core has an annular tire diameter in which six bead wires having a rectangular cross-sectional shape are arranged in parallel in the tire width direction. It is constructed by winding in three stages in the direction. Detailed specifications of the pneumatic tire of Comparative Example 2 are as shown in Table 1.

  The pneumatic tire of Comparative Example 3 has the bead core shown in FIG. 7 in the bead portion, and six bead wires arranged in parallel in the tire width direction are annularly wound in nine stages in the tire radial direction. It is composed. The cross-sectional shape of the bead wire is substantially arrow-shaped, and has an engaging portion that complements and engages between adjacent bead wires. Detailed specifications of the pneumatic tire of Comparative Example 3 are as shown in Table 1.

(Pressure resistance test)
In the pressure resistance test, air was introduced into the tire until the tire failed, and the pressure at the time of the failure was measured and compared. The measurement results show the pressure resistance per unit volume of the bead core as an index with Comparative Example 1 being 100, and the larger the value, the higher the pressure resistance performance per unit volume of the bead core. The results are shown in Table 2. All failures were due to the bead wire being cut.

  From the results shown in Table 2, it was confirmed that the application of the present invention improves the pressure resistance per unit volume of the bead core, that is, the desired pressure resistance can be obtained even if the amount of bead wire used is reduced. . Furthermore, it was confirmed that the pressure resistance performance is further improved by providing the engaging portion on the bead wire.

  According to the present invention, it is possible to improve the pressure resistance performance in a pneumatic tire provided with a bead core formed by winding a plurality of bead wires arranged in parallel in an annular shape, thereby reducing the weight while ensuring the safety of the tire. Has become feasible.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Bead core 4 Carcass 5 Bead wire 6 Engagement part

Claims (2)

A pair of bead portions, a pair of sidewall portions extending outward in the tire radial direction from the bead portions, and a tread portion extending between both sidewall portions are arranged in each bead portion in parallel in the tire width direction. In a pneumatic tire formed by arranging bead cores each formed by winding a plurality of bead wires in a plurality of stages in an annular shape,
In the cross section in the tire width direction, the vertical thickness of the bead wire is A (mm), the vertical thickness of the bead core is H (mm), the distance from the tire axis to the outermost position in the tire radial direction of the bead core is B (mm), When the distance from the rim axis of the applicable rim that matches the pneumatic tire to the outermost position in the rim radial direction of the rim flange is C (mm),
H / A ≧ 4 and
C + 5 (mm) ≧ B
Pneumatic tire characterized by satisfying   2. The pneumatic tire according to claim 1, wherein each bead wire constituting the bead core has an engaging portion that complementarily engages with each other between bead wires adjacent in the tire width direction.

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