JP4696743B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which the breaking strength of a bead core composed of a strand having a rectangular cross section is improved without unnecessarily increasing the number of caulking fittings for binding the bead core.

  In the bead core embedded in the bead portion of the pneumatic tire, a steel wire having a circular cross section is arranged in a row and covered with rubber, and this is continuously wound into an annular shape to form a multilayer wound bead core, A single-winding bead core is known in which a single steel wire having a circular cross section coated with rubber is continuously wound spirally and arranged in a row, and this is wound in multiple layers from an inner layer to an outer layer.

  As described above, these bead cores are wound while covering the steel wires with rubber in the molding stage and restraining the movement between the wires. That is, if each steel wire is not covered with rubber, the steel wire easily moves between the steel wires in the molding stage, the cross-sectional shape of the bead core after molding becomes unstable, and the load sharing of each steel wire is reduced. This is because it becomes non-uniform and it becomes difficult to function as a bead core.

  However, this coated rubber, on the other hand, increases the rigidity of the bead core in the vulcanized tire, and thus has a problem of deteriorating rim assembly. Especially in the case of large bead cores used for heavy duty tires, etc., since the bead core rigidity increases more and more, the bead portion in the tire after vulcanization becomes extremely stiff and the rim assemblability is significantly deteriorated. There was a problem to do.

  As a countermeasure, it has been proposed that a steel wire is formed into a rectangular cross section, arranged in a horizontal row without rubber covering, and formed into a belt-like body, and this belt-like body is wound to form an annular bead core (for example, Patent Document 1). In this type of bead core, since the steel wire has a rectangular cross section, each steel wire is focused by bringing the side surfaces into contact with each other, so that the shape of the bead core after molding is relatively stable even without rubber coating. There are advantages. In addition, when assembling the rim, each steel wire deforms while sliding the sides side by side, so there is flexibility as a bead core, making the rim assemblability remarkably good even for heavy duty tires that use large bead cores. It was a thing.

  However, the bead core that is actually used in the market prevents the breakage due to the steel wire circumferential expansion (break) at the time of tire molding, and maintains a more stable bead core shape as shown in FIG. ), A plurality of places on the circumference of the bead core 6 have been used by binding them with a crimping tool 7. Furthermore, since the bead core 6 is easily broken at the portion Q where the winding start end 6a and the winding end end 6b of the bead core 6 wrap (hereinafter referred to as the overlapping region Q), the interval between the crimping tools 7 in the overlapping region Q is increased. As shown in FIG. 6 (b), some devices are devised such as dense.

However, since the weight balance in the circumferential direction of the bead core 6 is lost and the uniformity is deteriorated when the number of the fasteners 7 is increased, the number of the fasteners 7 is substantially reduced as compared with the prior art. However, it is an issue to maintain the breaking strength of the bead core without increasing it.
JP-A 49-119301

  An object of the present invention is to solve such a conventional problem, and to improve the breaking strength of a bead core composed of a strand having a rectangular cross section without increasing the number of caulking fittings for binding the bead core. It is to provide a pneumatic tire.

  In order to achieve the above object, a pneumatic tire of the present invention is formed by winding a strip of steel wire strands having a rectangular cross-section in a horizontal row to form an annular body, and on the circumference of the annular body. In a pneumatic tire in which a plurality of locations are bundled with a caulking tool to constitute a bead core, and the bead core is embedded in a pair of left and right bead portions, the arrangement interval of the caulking tool is set to the winding start end of the belt-shaped body. In the overlapping region where the winding end and the winding end overlap, the end region on the winding end side corresponding to 1/2 of the circumferential length L of the overlapping region is made denser than the arrangement interval in the other regions. It is characterized by that.

  According to the present invention, a bead core is formed by winding a plurality of times a band-shaped body in which steel wire strands having a rectangular cross section are arranged in a horizontal row to form an annular body, and binding a plurality of locations on the circumference with a crimping tool. And the winding interval is equal to 1/2 of the circumferential length L of the overlapping region of the overlapping region where the winding start end and the winding end end of the belt-like body wrap. In the end region, the spacing between the other regions is higher than that of the other regions. The breakage of the bead core can be effectively prevented without unnecessarily increasing the number of tools.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  1 is a half sectional view showing an example of a pneumatic tire according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view showing a bead core in the tire of FIG. 1, and FIG. 3 is a bead of the tire of FIG. It is a side view which takes out and shows the bead core embed | buried under the part.

  In FIG. 1, a pneumatic tire 1 includes a pair of left and right bead portions 2 and 2, side wall portions 3 and 3 extending radially outward from the bead portions 2 and 2, and the side wall portions, respectively. A cylindrical tread portion 4 that connects the outer sides in the radial direction is provided.

  A bead core in which a carcass layer 5 is mounted between a pair of left and right bead portions 2 and 2, and both end portions 5 a and 5 a of the carcass layer 5 are embedded in the bead portions 2 and 2, respectively. 6 and 6 are folded back from the inside to the outside of the tire.

  As shown in FIGS. 2 and 3, the bead core 6 is composed of an annular body 6w formed by winding a strip of steel wire strands w having a rectangular cross-section in a horizontal row. A plurality of locations on the circumference of 6w are bundled by the crimping tool 7.

  And the arrangement | positioning space | interval K of the crimping tool 7 is set to 1 of the circumferential direction length L (illustration omitted) of this duplication area | region Q among the duplication area | regions Q where the winding start end 6a and the winding end end 6b of a strip | belt-shaped body wrap. In the termination region P on the winding end 6b side corresponding to / 2, it is denser than the arrangement interval K in the other regions. In the figure, S indicates the start end region on the winding start end 6a side excluding the end region P in the overlap region Q.

  As a result, even if the bead core 6 receives a tensile force from the carcass layer 5 as the tire internal pressure increases, the crimping tools 7 that narrow the arrangement interval of the stress applied to the crimping tool 7 concentrated on the terminal region P are respectively provided. Since the burden is shared, it is possible to effectively prevent the bead core 6 from breaking without unnecessarily increasing the number of the crimping tools 7. In addition, since the caulking tool 7 is arranged to be concentrated on a very small part of the end region P of the bead core 6, the collapse of the weight balance in the circumferential direction of the bead core 6 is minimized, and the uniformity is deteriorated. I will not let you.

  In the present invention, the circumferential length L of the overlapping region Q may be set to be 1.0 to 1.4 times the inner peripheral radius R in the overlapping region Q of the annular body 6w (1.0 ≦ L / R ≦ 1.4). If L / R is less than 1.0, the circumferential length L of the overlapping region Q is insufficient, so that the breaking strength of the bead core 6 is reduced. If it exceeds 1.4, the weight balance in the circumferential direction of the bead core 6 is decreased. As a result, the effects of the present invention may not be sufficiently obtained. In addition, the circumferential direction length L of the overlapping region Q in the present invention refers to the inner peripheral length in the overlapping region Q of the annular body 6w.

  Further, the number of the crimping tools 7 disposed in the terminal region P is set to 3 or more, and the spacing K between the crimping tools 7 is set to 0.05 to 0. 0 of the inner peripheral radius R in the overlapping region Q of the annular body 6w. It may be set to be 20 times (0.05 ≦ K / R ≦ 0.20). If K / R is less than 0.05, the weight balance in the circumferential direction of the bead core 6 will deteriorate, and if it exceeds 0.20, the breaking strength of the bead core 6 will decrease, so the effects of the present invention will be sufficiently obtained. There may not be.

  Moreover, in the termination | terminus area | region P, it is good to set the space | interval of the crimping tool 7 located in the most winding end 6b side, and the winding end 6b to 0-30 mm. Thereby, the fracture | rupture of the bead core 6 can be prevented reliably.

  In this case, the arrangement interval K of the crimping tool 7 in the normal region T (see FIG. 3) excluding the overlapping region Q described above is 0.40 to 0.60 times the inner peripheral radius R ′ in the normal region T. It is good to set so that it may become (0.40 <= K / R '<= 0.60). Thereby, the weight balance in the circumferential direction of the bead core 6 can be maintained appropriately.

  FIG. 4 is a partial side view showing an enlarged overlapping region Q of the bead core 6 according to another embodiment. The arrangement interval K of the crimping tool 7 in the terminal region P is changed from the winding end 6b side to the winding start end 6a side. I gradually try to make it bigger. By disposing the crimping tool 7 in this way, it is possible to efficiently suppress a decrease in the breaking strength of the bead core 6.

  In the present invention, the crimping tool 7 may be made of a material selected from steel, tungsten, molybdenum, or an alloy containing at least one of them. Thereby, the breaking strength of the crimping tool 7 can be secured and the breaking strength of the bead core 6 can be further improved.

  As described above, the pneumatic tire of the present invention is formed into an annular body by winding a strip of steel wire strands having a rectangular cross section in a horizontal row, and adding a plurality of locations on the circumference. The bead core is configured by binding with a fastener, and the arrangement interval of the crimping tool in the bead core is set to the circumferential length L of the overlap region of the overlap region where the winding start end and the winding end end of the belt-like body are wrapped. In the end region on the winding end side corresponding to 1/2, the breaking strength of the bead core is improved by making it denser than the arrangement interval in the other regions, and particularly a heavy load using a large bead core. It is preferably applied to heavy duty tires.

Each area (P, S, T) of the bead core shown in FIG. 2, with the tire core (11R22.5), the tire structure (FIG. 1), and the configuration of the bead core except for the arrangement of the crimping tools in common. Conventional tires (conventional examples 1 and 2) and tires of the present invention (examples) in which the ratio between the arrangement interval K of the crimping tool and the inner peripheral radii R and R 'of the annular body are different as shown in Table 1. Produced. In addition, the specification of the bead core in each tire was set as follows.
(1) Material of steel wire element: Steel (2) Sectional shape of steel wire element: rectangle (length = 1.3 mm, width = 2.0 mm)
(3) Cross-sectional shape of bead core: rectangle (4) Number of steel wire strands in cross-section of bead core: length (number of layers) = 6, width (number of rows) = 8)

  With respect to these three types of tires, a water pressure test was conducted by the following method to measure the water pressure at which the bead portion broke, and the result is shown in FIG. The results are shown in Table 1 by index. The larger the value, the higher the fracture strength of the bead part.

(Water pressure test)
When each tire is assembled in a rim (size: 11R22.5) and fixed in a water tank, and pressurized water is injected from the valve hole while applying pressure until the bead part breaks. When the bead part breaks The water pressure of was measured.

  As shown in the results of Table 1, it can be seen that the inventive tire has an improved fracture strength at the bead portion compared to the conventional tire.

1 is a half sectional view showing an example of a pneumatic tire according to an embodiment of the present invention. It is sectional drawing which expands and shows the bead core in the tire of FIG. It is a side view of the bead core which takes out and shows a bead core from the tire of FIG. It is a partial side view which expands and shows the principal part of the bead core by other embodiment of this invention. It is a graph which shows the result of the water pressure test with the conventional tire and this invention tire in the Example of this invention. (A) And (b) is a side view which shows the form of the conventional bead core, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 4 Tread part 5 Carcass layer 6 Bead core 6a Winding start edge 6b Winding end edge 6w Annular body 7 Clamping tool w Steel wire strand Q Overlapping area P End area S Start area T Normal area

Claims (6)

A belt-shaped body in which steel wire wires having a rectangular cross section are arranged in a horizontal row is wound a plurality of times to form an annular body, and a plurality of locations on the circumference of the annular body are bound by a crimping tool to form a bead core. In the pneumatic tire in which the bead core is embedded in a pair of left and right bead parts,
The winding end side corresponding to ½ of the circumferential length L of the overlapping region of the overlapping region where the winding start end and the winding end end of the belt-like body wrap are arranged at intervals of the crimping tool. A pneumatic tire characterized in that the end region of the tire is denser than the arrangement interval in other regions.   The pneumatic tire according to claim 1, wherein a circumferential length L of the overlapping region is 1.0 to 1.4 times an inner peripheral radius R in the overlapping region of the annular body.   The number of the fasteners arranged in the terminal region is set to 3 or more, and the arrangement interval K of the fasteners is 0.05 to 0.20 times the inner peripheral radius R in the overlapping region of the annular body. The pneumatic tire according to claim 1 or 2.   The pneumatic tire according to claim 1, 2, or 3, wherein an arrangement interval of the crimping tool in the terminal region is gradually increased toward the winding start end side.   The pneumatic tire according to any one of claims 1 to 4, wherein the crimping tool is made of a material selected from steel, tungsten, molybdenum, or an alloy containing at least one of them. The pneumatic tire according to any one of claims 1 to 5, which is a heavy load tire.

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