JP2011136668A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress blow-by of a carcass ply while reducing the weight of a tire. <P>SOLUTION: A bead core 5 includes an outermost core piece and an inner core piece on the inner side divided into two portions in the tire radial direction. An inner surface in the tire radial direction of the outer core piece and an outer surface in the tire radial direction of the inner core piece are arranged substantially opposite to each other with a small space therebetween over the maximum width in the tire axial direction of the bead core 5. An end portion 11 of a carcass ply extends from one end side in the tire axial direction and is terminated at the other end in the tire axial direction of the bead core 5 through the small space. Further, in the tire meridian section including the tire rotational axis, the small space has at least two bent parts for bending the end portion 11 of the carcass ply at substantially 90°. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that can prevent a carcass ply from being blown through while reducing the weight of the tire.

  Conventionally, as shown in FIG. 8 (a), a carcass a forming a skeleton of a pneumatic tire usually has a body portion p1 extending in a toroidal shape between bead cores b and b and a non-extensible bead core b. It includes one carcass ply p integrally having a folded portion p2 folded from the inner side to the outer side in the tire axial direction. The folded portion p2 of the carcass ply p extends to the outer surface position of the bead apex c in the tire axial direction or the position beyond the outer end of the bead apex c. FIG. 8B shows an example in which the carcass ply p is two.

  In the pneumatic tire as described above, since the folded portion p2 of the carcass ply p is in contact with the bead core b and the bead apex c in a wide range, the folded portion p2 of the carcass ply is on the main body portion p1 side due to internal pressure and / or load load. High resistance to so-called blow-through moving to However, the folded portion p2 having a large length causes an increase in tire mass, and also has a problem that distortion tends to concentrate on the outer end thereof and becomes a starting point of damage such as loose.

  Therefore, as shown in FIG. 9A, a bead structure is proposed in which the bead core b is divided into a plurality of parts, and the end portion p3 of the carcass ply p is bent and sandwiched therebetween. Such a bead structure is effective in reducing the weight of the tire because the folded portion can be eliminated. However, this bead structure has a drawback that blow-through is likely to occur because the contact area between the end portion p3 of the carcass ply and the bead core b is small. Further, when an internal pressure or a large tension acts on the main body portion p1 of the carcass ply p, the bead apex c is easily peeled off from the bead core b, and there is a difficulty in durability.

  Further, as shown in FIG. 9 (b), a bead structure in which the bead core b is divided in the tire axial direction and the end portion p4 of the carcass ply p is sandwiched therebetween is proposed. However, such a bead structure has a drawback that blow-through easily occurs because the tension acting on the main body portion p1 of the carcass ply p acts on the end portion p4 as it is.

Japanese Patent Laid-Open No. 2005-112075 JP 2004-9894 A

  The present invention has been devised in view of the above problems, and the bead core is composed of an outer outer core piece divided into two in the tire radial direction and an inner core piece on the inner side. And forming a small gap across the maximum width of the bead core between which the end portion of the carcass ply is inserted, and at least two portions where the end portion of the carcass ply is bent at substantially 90 degrees. The main object is to provide a pneumatic tire capable of preventing the carcass ply from being blown out while reducing the weight based on the provision of the bent portion.

  The invention according to claim 1 of the present invention is a pneumatic tire comprising a carcass having at least one carcass ply which is locked by a bead core of a bead part from a tread part through a sidewall part, and the bead core Includes an outermost outer core piece divided into at least two in the tire radial direction and an inner core piece on the inner side thereof, a tire radial inner surface of the outer core piece, and a tire radius of the inner core piece The outer side surface is arranged to face each other with a small gap substantially across the maximum width of the bead core in the tire axial direction, and the end portion of the carcass ply has the small gap from one end side in the tire axial direction. In the tire meridian section including the tire rotation axis, the small gap is formed in front of the carcass ply. The end portions, and having a bent portion of the at least two locations bent at substantially 90 degrees.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the end portion of the carcass ply terminates at the outer end in the tire axial direction of the bead core from the inner side in the tire axial direction through the small gap.

  The invention according to claim 3 is the pneumatic tire according to claim 1, wherein the end portion of the carcass ply terminates at the inner end in the tire axial direction of the bead core from the outer side in the tire axial direction through the small gap.

  The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein the inner core piece and the outer core piece are each formed by winding a steel wire.

  In the invention according to claim 5, the carcass includes two carcass plies, and the bead core is divided into three in the tire radial direction, whereby the outer core piece, the inner core piece, The inner core piece is disposed on the inner side of the inner core piece, and the inner side surface of the inner core piece in the tire radial direction and the outer side surface of the sub core piece in the tire radial direction are the outermost side of the bead core in the tire axial direction. The end portions of at least one carcass ply are arranged so as to face each other across a second small gap over a large distance, and pass through the second small gap from one end side in the tire axial direction. In the tire meridian cross section including the tire rotation axis, the second small gap has at least two ends that bend the end portion of the carcass ply substantially at 90 degrees. A pneumatic tire according to any one of claims 1 to 4 having a bent portion.

  According to a sixth aspect of the present invention, the end portion of the at least one carcass ply terminates from the inner side in the tire axial direction through the second small gap at the outer end in the tire axial direction of the second small gap. The pneumatic tire according to claim 5.

  According to a seventh aspect of the present invention, the end portion of the at least one carcass ply terminates from the outer side in the tire axial direction through the second small gap at the inner end in the tire axial direction of the second small gap. The pneumatic tire according to claim 5.

  In the present invention, the bead core includes an outermost outer core piece divided into at least two in the tire radial direction and an inner core piece on the inner side, and the inner radial side surface of the outer core piece and the inner core piece. Are substantially opposed to each other with a small gap extending across the maximum width of the bead core in the tire axial direction. The end portion of the carcass ply terminates from the inner side in the tire axial direction through the small gap at the outer end in the tire axial direction of the small gap. Thereby, since the folding | turning part of a carcass ply can be eliminated, a tire can be reduced in weight.

  In the tire meridian cross section including the tire rotation axis, the small gap of the bead core has at least two bent portions that bend the end portion of the carcass ply substantially at 90 degrees. In this manner, by providing two bent portions in the bead core, the end portion of the carcass ply is fixed with a large contact length in the bead core, so that it is possible to show a high resistance to blow-through. .

It is sectional drawing of the right half which shows the pneumatic tire of one Embodiment of this invention. It is an enlarged view of the bead part of FIG. It is an expanded sectional view of the bead core. (A), (b) is sectional drawing explaining the formation method of the bead structure of this embodiment. (A), (b) is the cross-sectional schematic of the bead part which shows other embodiment of this invention. It is the cross-sectional schematic of the bead part which shows other embodiment of this invention. It is the cross-sectional schematic of the bead part which shows other another embodiment of this invention. (A), (b) is sectional drawing of the conventional bead part. (A), (b) is sectional drawing of the conventional bead part.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic tire (hereinafter, simply referred to as “tire”) 1 according to this embodiment is engaged with a bead core 5 of a bead portion 4 from a tread portion 2 to a sidewall portion 3. A carcass 6 having a stopped carcass ply 6A, a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2, and a taper shape radially outward from the tire radial outer surface of the bead core 5. In this embodiment, a regular state of a radial tire for a passenger car is shown. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values in this normal state.

  The normal state is a no-load state in which the tire 1 is assembled on a normal rim and filled with a normal internal pressure. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA. "Or, if ETRTO," Measuring Rim ". The “regular internal pressure” is the air pressure defined by the standard for each tire, and is “maximum air pressure” for JATMA, and “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA. If the maximum value is ETRTO, “INFLATION PRESSURE” is set, and if the tire is for a passenger car, it is uniformly set to 180 kPa.

  The belt layer 7 is composed of two outer belt plies 7A and 7B, in which a belt cord (not shown) made of, for example, steel is inclined with respect to the tire equator C at an angle of, for example, 15 to 45 °. The belt plies 7A and 7B are overlapped so that the steel cords cross each other.

  The carcass 6 includes a layer of a carcass cord 6c in which a toroid-like main body portion 10 straddling the bead cores 5 and 5 and an end portion 11 connected to the main body portion 10 and locked by the bead core 5 are provided in series. It is composed of at least one (in this embodiment, one) carcass ply 6A.

  As shown in FIG. 2, the carcass ply 6A is composed of an array of carcass cords 6c arranged in parallel and a topping rubber 6G covering both sides thereof. The carcass ply 6A is arranged such that the carcass cord 6c is at an angle of, for example, 80 to 90 ° with respect to the tire equator C. For the carcass cord 6c, an organic fiber cord such as nylon, polyester, rayon or aromatic polyamide is suitably employed.

  As shown in an enlarged view in FIG. 2, the bead core 5 includes an outermost outer core piece 5a divided into at least two in the tire radial direction, in this embodiment, and an inner core piece 5b on the inner side. It consists of.

  In the present embodiment, each outer core piece 5a and inner core piece 5b is formed by winding a bead wire 5w in which the outer peripheral surface of a steel wire 5s having a circular cross section made of steel is covered with a bead coating rubber 5G in multiple stages and multiple rows. It is formed as a predetermined cross-sectional shape.

  Further, steel strands 5s having the same wire diameter are used for the outer core piece 5a and the inner core piece 5b, respectively. In the case of a radial tire for passenger cars, the wire diameter is preferably about 0.8 to 1.60 mm. However, the material and / or wire diameter of the steel strand 5s may be different between the outer core piece 5a and the inner core piece 5b as necessary. Moreover, each core piece 5a, 5b may be an integrally molded product of a steel material other than the wound body of the bead wires 5w.

FIG. 3 shows an enlarged cross-sectional view of the bead core 5 of FIG.
As shown in FIG. 3, the outer side surface 5by in the tire radial direction of the inner core piece 5b is positioned on the outer side in the tire axial direction of the large outer diameter portion 12 positioned on the outer side in the tire axial direction. And it is comprised including the small outer diameter part 13 of an outer diameter smaller than a large outer diameter part, and the level | step difference surface 14 which connects between these.

  The small outer diameter portion 13 is a portion having an outer diameter DA formed by a tangent drawn to the outermost surface of the steel strand 5s of the bead wire 5w wound in two steps in the tire radial direction. The large outer diameter portion 12 is a portion having an outer diameter D1 formed by a tangent drawn to the outermost surface of the steel element wire 5s of the bead wire 5w wound by one round more than the small outer diameter portion 13. The inner step surface 14 is a tire radial direction line that contacts the innermost steel strand 5s of the large outer diameter portion 12 in the tire axial direction and connects the small outer diameter portion 13 and the large outer diameter portion 12. Therefore, 1/2 of the outer diameter difference (D1-DA) is formed to be approximately equal to or slightly larger than the steel wire diameter of the bead wire 5w.

  Further, the inner side surface 5ax in the tire radial direction of the outer core piece 5a has a large inner diameter portion 15 facing the large outer diameter portion 12 of the inner core piece 5b, and is located on the inner side in the tire axial direction of the large inner diameter portion 15 and A small inner diameter portion 16 that faces the small outer diameter portion 13 of the core piece 5b and an outer stepped surface 17 that connects between them are configured.

  The small inner diameter portion 16 is a portion having an inner diameter D2 formed by a tangent drawn to the innermost side surface of the steel strand 5s of the innermost bead wire 5w among the bead wires 5w wound in three stages in the tire radial direction. The large inner diameter portion 15 is formed by reducing the number of turns of the inner layer by one step as compared with the small inner diameter portion 16, and the inner diameter DB formed by the tangent drawn on the innermost side surface of the steel strand 5s of the innermost bead wire 5w. It is a part which has. Therefore, ½ of the difference in inner diameter (DB−D2) is also approximately equal to or slightly larger than the steel wire diameter of the bead wire 5w.

  2 and 3, the large inner diameter portion 15 of the outer core piece 5a is provided on the inner side in the tire axial direction. Accordingly, a large frictional force is exerted against the tension acting on the main body portion 10 of the carcass ply 6A to prevent blow-through, and the length of the end portion 11 of the carcass ply 6A is made as short as possible.

  Further, the inner side surface 5ax of the outer core piece 5a and the outer side surface 5by of the inner core piece 5b are arranged facing each other with a small gap S extending substantially over the maximum width BW of the bead core 5 in the tire axial direction. Is done. In order to provide the small gap S, the outer core piece 5a and the inner core piece 5b of the bead core 5 face each other with a positional deviation amount d in the tire axial direction. In the present specification, “substantially” extending over the maximum width BW of the bead core 5 in the tire axial direction means that the small gap S has a length equal to the maximum width BW of the bead core 5 in the tire axial direction. In addition to the aspect, the case where the length is a length obtained by subtracting the positional deviation amount d from the maximum width BW is included.

  In the small gap S, an end portion 11 of the carcass ply 6A is inserted from one end side in the tire axial direction of the bead core 5 (in the tire axial direction inner side in this embodiment), and the end portion 11 is in the tire axial direction of the bead core 5 Is terminated at the other end (outer end in this embodiment) St. Such a carcass ply 6A can eliminate the folded portion, and thus can be reduced in weight as compared with a conventional tire.

  In the tire meridian cross section including the tire rotation axis, the small gap S has at least two bent portions 9 and 9 that bend the end portion 11 of the carcass ply 6A substantially at 90 degrees, in this embodiment, two bent portions 9 and 9. It has a crank shape with As a result, the end portion 11 of the carcass ply 6A is sandwiched between the outer core piece 5a and the inner core piece 5b of the non-extensible bead core 5 that does not substantially deform under a large contact area. In addition, by forming a plurality of bent portions 9 inside the bead core 5, the engagement force between the end portion 11 of the carcass ply 6A and the bead core 5 is significantly increased. In particular, in order to effectively increase the engagement force, the bent portion 9 has a steel wire diameter of the bead wire 5w that is at least one span in the tire radial direction and / or at least in the tire axial direction as in this embodiment. It is desirable to bend as two spans.

  Further, when tension is applied to the main body portion 10 of the carcass ply 6A, the outer core piece 5a tries to rotate clockwise in the drawing, and at this time, the small inner diameter portion 16 of the outer core piece 5a A wedge action is obtained in which the end portion 11 of the carcass ply 6A is firmly sandwiched by approaching the small outer diameter portion 13 of the core piece 5b.

  Due to the synergistic effect of the actions described above, the pneumatic tire 1 of the present invention can exhibit a very large proof strength against the blow-through of the carcass ply 6A while reliably reducing the weight. In addition, according to the structure of the present invention, a phenomenon that the bead core 5 and the bead apex 8 are peeled off by the tension acting on the main body portion 10 of the carcass ply 6A does not occur.

  The end portion 11 of the carcass ply 6A extending through the small gap S is preferably compressed by the outer core piece 5a and the inner core piece 5b. In particular, the end portion 11 of the carcass ply 6A is preferably compressed by being sandwiched between the steel strands 5s and 5s through a rubber layer made of the topping rubber 6G and / or the coating rubber 5G. Thereby, the yield strength against blow-through can be further increased while preventing the carcass cord 6c from being broken or damaged.

Such a pneumatic tire 1 can be easily obtained, for example, by employing a manufacturing method in which the following formula is satisfied and molded and then vulcanized.
D1 + 2 × G0 <DB <D1 + 2 × G1 + 2 × (W1-W0) (1)
DA + 2 * G0 <D2 <DA + 2 * G1 + 2 * (W1-W0) (2)
Here, the symbols are as follows.
D1 ... Outer diameter of the large outer diameter portion of the inner core piece 5b DA ... Outer diameter of the small outer diameter portion of the inner core piece 5b D2 ... Inner diameter of the small inner diameter portion of the outer core piece 5a DB ... Large inner diameter portion of the outer core piece 5a Inner diameter G0: carcass cord outer diameter G1: thickness of uncured carcass ply (cord + topping rubber) W0: diameter of steel wire W1: diameter of bead wire That is, large outer diameter portion 12 of inner core piece 5b Is preferably smaller than the total thickness of the uncured carcass ply and the bead coating rubber, and larger than the outer diameter of the carcass cord. . The difference between the outer diameter of the small outer diameter portion 13 of the inner core piece 5b and the inner diameter of the small inner diameter portion 16 of the outer core piece 5a is smaller than the combined thickness of the unvulcanized carcass ply and the bead coating rubber. The outer diameter of the carcass cord is preferably larger.

  The bead structure of the pneumatic tire of the above embodiment can be easily formed by, for example, the method shown in FIG. That is, first, as shown in FIG. 4A, the carcass ply 6 </ b> A is wound around the cylindrical drum D in a cylindrical shape, and the end portion 11 is unwound along the end surface of the drum D. Next, the outer core piece 5a previously wound in a ring shape is brought into contact with the end portion 11 of the carcass ply 6A. And after winding up the edge part 11 along the inner surface 5ax of the outer core piece 5a, the inner core piece 5b is inserted from the tire axial direction outer side.

  5A and 5B show another embodiment of the present invention. In this embodiment, the carcass 6 includes two carcass plies 6A and 6B, and the bead core 5 is divided into three in the tire radial direction, the outer core piece 5a, the inner core piece 5b, and the inner core piece. It is comprised from the subcore piece 5c distribute | arranged to. Note that the engagement of the carcass ply 6A, the outer core piece 5a, and the inner core piece 5b is the same as in the above embodiment.

  Further, the inner side surface 5bx of the inner core piece 5b and the outer side surface 5cy in the tire radial direction of the sub core piece 5c are separated by a second small gap S1 extending over the maximum width BW of the bead core 5 in the tire axial direction. They are placed facing each other. Then, similarly to the carcass ply 6A, the end portion 11c of the carcass ply 6B terminates at the outer end St1 in the tire axial direction of the second small gap S1 from the inner side in the tire axial direction through the second small gap S1. In addition, in the tire meridian cross section including the tire rotation axis, the second small gap S1 has at least two bent portions 18 that bend the end portion 11c of the carcass ply at substantially 90 degrees. .

  In such an embodiment, both the folded portions of the two carcass plies 6A and 6B can be eliminated, so that a very large weight saving merit can be enjoyed.

  FIG. 6 shows still another embodiment. In this embodiment, the large inner diameter portion 15 of the outer core piece 5a is provided on the outer side in the tire axial direction. As a result, the length L in the radial direction of the inner surface in the tire axial direction of the outer core piece 5a is increased, so that a larger frictional force is exerted against the tension acting on the main body portion 10 of the carcass ply 6A to prevent blowout. To help.

  FIGS. 7A and 7B show still another embodiment. In the embodiment of FIG. 7A, the end portion 11 of the carcass ply 6A is inserted from the outside of the bead apex 8 in the tire axial direction. 7B, the end portions 11 of the carcass plies 6A and 6B are also inserted from the outside in the tire axial direction of the bead apex 8.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.

  Pneumatic tires of size 185 / 60R14 having a bead core structure shown in each table shown in Tables 1 and 2 were made on the basis of the specifications in Table 1 and tested for bead strength and carcass mass. The internal structure other than the tire bead core structure and the tread rubber were all the same. Each specification is as follows.

Diameter of steel strand: 0.96mm
Coating rubber thickness: 0.12mm
Bead wire outer diameter: 1.2 mm (before vulcanization)
Total number of bead wires appearing in the tire meridian section: 20 Carcass cord material: Polyester Carcass cord outer diameter: 1.1 mm
In addition, the tire of an Example is manufactured by satisfying said Formula (1) and (2). The test method is as follows.

<Bead strength>
The tire was assembled with a rim (22.5 × 7.50 V), the tire lumen was filled with water from the valve, and the breaking water pressure when the tire burst was measured. For Table 1, Comparative Example 1 is shown, and for Table 2, Comparative Example 4 is shown as an index of 100. The larger the value, the better. Moreover, 80 or more was set as the pass.

<Carcass mass>
The mass of the carcass per tire was measured, and displayed as an index with Comparative Example 1 as 100. The smaller the value, the better.
Table 1 shows the test results for one carcass ply and Table 2 shows the test results for two carcass plies.

  As a result of the test, it was confirmed that the examples had a carcass mass smaller than that of the comparative example and passed the bead strength test. Further, when the sample of Comparative Example 3 was disassembled after completion of the test, it was confirmed that the bead apex rubber had fallen down.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 5a Outer core piece 5b Inner core piece 5ax Tire radial inner side surface 5by of outer core piece Tire radial outer side face 6 of inner core piece 6 Carcass 6A Carcass ply 11 End portion 9 of carcass ply Bending portion S Small gap St The outer end of the bead core in the tire axial direction

Claims (7)

A pneumatic tire comprising a carcass having at least one carcass ply that is locked with a bead core of a bead portion from a tread portion through a sidewall portion,
The bead core includes an outermost outer core piece divided into at least two in the tire radial direction, and an inner core piece on the inner side.
A tire radial inner side surface of the outer core piece and a tire radial outer side surface of the inner core piece are arranged to face each other with a small gap substantially across the maximum width of the bead core in the tire axial direction. ,
The end portion of the carcass ply terminates at the other end in the tire axial direction of the bead core through the small gap from one end side in the tire axial direction,
In a tire meridian section including a tire rotation axis, the small gap has at least two bent portions that bend the end portion of the carcass ply substantially at 90 degrees.   The pneumatic tire according to claim 1, wherein an end portion of the carcass ply terminates at an outer end of the bead core in the tire axial direction from the inner side in the tire axial direction through the small gap.   2. The pneumatic tire according to claim 1, wherein the end portion of the carcass ply terminates from the outer side in the tire axial direction through the small gap at the inner end in the tire axial direction of the bead core.   The pneumatic tire according to any one of claims 1 to 3, wherein each of the inner core piece and the outer core piece is formed by winding a steel wire. The carcass consists of two carcass plies,
The bead core is composed of the outer core piece, the inner core piece, and the sub-core piece arranged inside the inner core piece by being divided into three in the tire radial direction,
A tire radial inner side surface of the inner core piece and a tire radial outer side surface of the sub core piece are arranged to face each other with a second small gap across the maximum width of the bead core in the tire axial direction. ,
The end portion of at least one carcass ply terminates at the other end in the tire axial direction of the second small gap through the second small gap from one end side in the tire axial direction,
5. The tire meridian section including the tire rotation axis, wherein the second small gap has at least two bent portions that bend the end portion of the carcass ply substantially at 90 degrees. Pneumatic tire described in 2.   The pneumatic tire according to claim 5, wherein an end portion of the at least one carcass ply terminates from an inner side in the tire axial direction through the second small gap at an outer end in the tire axial direction of the second small gap. .   The pneumatic tire according to claim 5, wherein an end portion of the at least one carcass ply terminates at an inner end in the tire axial direction of the bead core from the outer side in the tire axial direction through the small gap.

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