JP2006341807A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To largely reduce weight by enhancing the freedom of a carcass line on the assumption that the durability of a bead of a tire having a clamping-in bead structure is maintained. <P>SOLUTION: The pneumatic tire is provided with a pair of beads 1; a carcass ply for rubber-covering a ply cord; and a pair of bead cores 2a, 2b buried in the bead 1 and clamping the carcass ply 4 by a pair of opposed surfaces 3a, 3b. One bead core 2a is positioned at an outer side in the tire radial direction of the other bead core 2b. The surfaces 3a, 3b of the bead cores 2a, 2b for clamping the carcass ply have at least one of bent parts 5a-7a, 5b-7b, respectively, and are in a complementary relationship mutually. The carcass ply 4 toroidally extends between both beads and enters from an outer side in a tire width direction to a gap between the bead cores 2a, 2b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a pneumatic tire having a pair of bead portions and a ply cord covered with rubber and extending in a toroidal shape between the pair of bead portions, in particular, a carcass ply is sandwiched between a pair of bead cores. The present invention relates to a pneumatic tire having a bead portion structure, that is, a so-called sandwich bead structure, and the weight is reduced on the premise that the durability of the bead portion of the tire is maintained.

  In general pneumatic tires, a carcass ply is formed around the bead core having sufficient circumferential rigidity in order from the inside to the outside in the tire width direction in order to prevent the carcass from being pulled out during tire rolling. The carcass ply is firmly fixed to the bead core by embedding the end portion of the carcass ply in a rubber member on the outer side of the rim line in the tire radial direction. In such a prior art, the end portion of the carcass ply is positioned on the outer side in the tire radial direction from the contact area of the bead portion with the rim, and the bead portion or the sidewall portion where the end portion is located Unlike the radially inner end portion of the bead portion that is firmly held by the rim and is strongly reinforced by the bead core, the bead filler, etc., the tire is positioned on the outer side in the tire radial direction than the rim flange surface when rolling the tire. The part falls down toward the outside in the tire width direction and repeats deformation. As a result, stress tends to concentrate particularly on the end portion of the carcass ply, and separation may occur from the stress, which may proceed along the folded portion of the carcass ply. In such a tire, since the carcass ply is disposed so as to wrap the bead core, the degree of freedom of the so-called carcass line, which is a line connecting the path of the carcass ply or the thickness center position of the carcass ply in the cross section in the tire width direction. However, the case thickness at the bead portion was inevitably increased.

  In order to prevent such separation from the carcass ply end and increase in case thickness, for example, in Patent Document 1, as shown in FIG. 10, a pair of left and right beads are divided into left and right in the tire width direction. And a bead core that meshes the two split surfaces with each other, the carcass ply is mounted on the pair of left and right bead portions, and the end of the carcass ply is inserted between the split surfaces of the bead core. A pneumatic radial tire sandwiched between split surfaces is described.

JP 2002-67629 A

  However, in the pneumatic tire having the structure described in Patent Document 1, the case thickness of the bead portion is reduced compared to a pneumatic tire having a conventional structure in which the carcass ply is folded around the bead core. Although weight reduction has been achieved, the arrangement of the carcass line is still limited, and it has been difficult to achieve further weight reduction.

  Therefore, the present invention aims to solve such problems of the prior art, the purpose is to maintain the durability of the bead portion of the tire having a sandwich bead structure, The purpose is to increase the degree of freedom of the carcass line and to reduce the weight significantly.

  In order to achieve the above object, the present invention provides a pair of bead parts, a carcass ply formed by covering a ply cord with rubber, and a pair of the carcass ply sandwiched between a pair of opposing surfaces embedded in the bead part. In the pneumatic tire including the bead core, one bead core is positioned on the outer side in the tire radial direction of the other bead core in the tire width direction cross section, and each of the surfaces sandwiching the carcass ply of each bead core has at least one The carcass ply has a bent portion and is complementary to each other, and the carcass ply extends in a toroid shape between both bead portions and enters between the pair of bead cores from the outer side in the tire width direction. Tire. By adopting such a configuration, when the tension is applied to the carcass ply due to the internal pressure filled in the tire and the deformation of the tread portion during tire rolling, the carcass ply contacts the bent portion. As a result, the effect of locking the carcass ply by the bead core is enhanced, and there are few restrictions on the carcass line, so that the case thickness of the bead portion can be easily reduced.

  Further, the sandwiching surface of each bead core preferably has at least two bent portions, and is preferably formed by alternately arranging convex bent portions and concave bent portions, and the bent width is the tire width from the outer side in the tire width direction. More preferably, the taper gradually decreases inward in the direction. The “bending width” here means a distance between two bending portions adjacent to a certain bending portion or an imaginary line connecting the bending portion and the end of the holding surface and the bending portion.

  Furthermore, it is preferable that the carcass ply is positioned on the outer side in the tire width direction than the center position in the tire width direction of the bead portion at the rim line position. The “rim line position” as used herein refers to an unloaded condition in which a tire is assembled to a standard rim at an applicable size described in JATMA or a standard equivalent thereto, and the maximum air pressure defined in the standard is applied in the tire. The range between the portion corresponding to the outermost end in the tire radial direction of the rim flange and the portion spaced 30 mm away from the outer side in the tire radial direction from here.

  Furthermore, it is preferable that the carcass ply includes a main body portion that extends in a toroidal shape between both bead portions and is sandwiched between each pair of bead cores, and a protruding portion that is connected to the main body portion and protrudes from the bead core. In this case, the protrusion is bent so that the end of the carcass ply faces outward in the tire radial direction, the protrusion is provided on at least the inner surface of the protrusion, and the protrusion is formed on the carcass ply. More preferably, it is covered with a rubber member having a 100% modulus equal to or greater than 100% modulus of the coated rubber.

  According to this invention, since the bead core has a bent portion, the effect of locking the carcass ply by the bead core is increased, so that the bead portion durability can be maintained at a high level, and the case thickness of the upper bead portion can be easily reduced. Can be significantly reduced in weight.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section in the tire width direction of a bead portion of a typical pneumatic tire (hereinafter referred to as “tire”) according to the present invention.

  A pair of bead cores 2a and 2b are embedded in the bead portion 1 so as to face each other. The bead cores 2a and 2b have high circumferential rigidity, and can have, for example, a so-called single-wind structure in which one rubber-coated bead wire is continuously wound in a spiral shape. The bead cores 2a and 2b sandwich the carcass ply 4 between their opposing surfaces 3a and 3b, thereby forming a so-called sandwich bead structure. The carcass ply 4 is configured by covering a ply cord with rubber, and extends in a toroid shape from a tread portion (not shown) to a bead portion 1 through a sidewall portion according to a custom. As the ply cord, an organic fiber cord such as nylon, rayon, polyester, and aromatic polyamide, and a metal cord such as steel are used in the same manner as the cord constituting the conventional carcass ply.

  One bead core 2a is located on the outer side in the tire radial direction of the other bead core 2b as a whole. The surfaces 3a and 3b sandwiching the carcass ply 4 of each bead core 2a and 2b each have at least one bent portion. In the embodiment shown in FIG. 1, the bead core 2a has three bent portions 5a, 6a and 7a. The bead core 2b has three bent portions 5b, 6b, and 7b. The sandwiching surfaces 3a and 3b are in a complementary relationship with each other. That is, concave bent portions 5b and 7b are disposed on the sandwiching surface 3b at portions facing the convex bent portions 5a and 7a of the sandwiching surface 3a, and the concave shape of the sandwiching surface 3a of the sandwiching surface 3b is disposed. A convex bent portion 6b is disposed at a portion facing the bent portion 6a, and when the sandwiching surfaces 3a and 3b are brought into contact with each other, they are in meshing relation. The carcass ply 4 extends in a toroidal shape between both bead portions, enters between the bead cores 2a and 2b from the outer side in the tire width direction, and is sandwiched along the sandwiching surfaces 3a and 3b of the bead cores 2a and 2b.

  The carcass ply is subjected to a tension T caused by the air filled in the tire or deformation of the tread portion during rolling of the tire load. However, particularly when the tension T is large, such as a heavy load tire, In the bead structure, the carcass ply may be pulled out of the bead core, resulting in an early failure. This is presumably because the extending direction of the carcass ply between the bead cores substantially coincides with the direction of action of the tension T, so that there is nothing to prevent the movement of the carcass ply and the force that resists the tension T is insufficient. Therefore, in the tire according to the present invention, at least one bent portion is provided on each of the sandwiching surfaces 3a and 3b of the bead cores 2a and 2b, and even when the tension T acts on the carcass ply 4 and the carcass ply 4 is pulled, the carcass ply 4 and the bent portions 5a, 5b, 6a, 6b, 7a and 7b are engaged to prevent the movement of the carcass ply 4 and improve the locking force to maintain the bead portion durability at a high level.

  However, simply providing a bent portion on the clamping surface improves the locking force, but it is difficult to achieve weight reduction because the degree of freedom of the carcass line is low. That is, in a tire in which a pair of bead cores are arranged side by side in the tire width direction as shown in FIG. 10, the carcass ply 4 enters between the bead cores 102 a and 102 b from the outer side in the tire radial direction. Therefore, there is a limit to weight reduction. On the other hand, in the tire of this invention, since the bead cores 2a and 2b are arranged side by side in the tire radial direction, the degree of freedom of the carcass line 4 is high, and the outer contour shape of the bead portion 1 is easily formed. be able to. As a result, since the inner contour shape of the bead portion 1 can be made substantially parallel to the outer contour shape thereof, the case thickness of the bead portion 1 is reduced, which is much higher than that of the tire shown in FIG. Light weight can be achieved.

  Moreover, it is preferable that the clamping surfaces 3a and 3b of the bead cores 2a and 2b have at least two bent portions, respectively, and the convex bent portions and the concave bent portions are alternately arranged. In the embodiment shown in FIG. 1, in the bead core 2a, the convex bent portion 5a, the concave bent portion 6a, and the convex bent portion 7a are arranged in this order. In the bead core 2b, the concave bent portion 5b and the convex bent portion 6b are arranged. The convex bent portions and the concave bent portions are alternately arranged in the order of the concave bent portions 7b. By setting it as such a structure, when many bending parts are provided, the increase in the thickness of bead core 2a, 2b can be suppressed. Further, even if the carcass ply 4 is pulled out from one bent portion, the next bent portion is bent in the opposite direction, so that the engagement between the next bent portion and the carcass ply is shaped. It becomes expensive and cannot be pulled out easily.

2 (a) and 2 (b) are diagrams showing the contour shapes of the bead cores 2a and 2b in FIG. 1, respectively. Bending width w ₁ at the bending point 5a of the bead core 2a includes a virtual line l ₁ connecting the tire width direction outer end portion 8a and the bent portion 6a of the clamping face adjacent thereto, aimed along a direction perpendicular thereto It is defined as a separation distance that is a distance from the bending point 5a. Further, the bent width _{w 2} in the bending portion 6a is a distance between the virtual line _{l 2} connecting the bent portions 5a and 7a bent portion 6a, bent width _{w 3} in the bending portion 7a is bent portion 6a and the holding surface virtual line l ₃ connecting the tire width direction inner end portion 9a of the a distance between the bent portion 6a. Similarly, the bending widths w ₄ , w ₅ , and w _{6 at} the bent portions 5b, 6b, and 7b are defined for the bead core 2b. Then, in this _{invention, w 1> w 2> w} 3 and _{w 4> w 5> w 6} the relationship it is preferable to hold. The force applied from the carcass to the bead core increases as the bead core moves outward in the tire radial direction. Thus, by gradually increasing the bending width from the inner side in the tire width direction toward the inner and outer side in the tire width direction, it is possible to obtain a high locking force and to effectively prevent the carcass from being pulled out.

The bending widths w _{1 to} w ₆ are preferably set to 1 mm or more from the viewpoint of securing the engagement with the carcass ply. However, since the case thickness of the bead part 1 will increase if the bending widths w _{1 to} w ₆ are excessive, it is preferably 5 mm or less from the viewpoint of weight reduction.

  Referring again to FIG. 1, the carcass ply 4 is preferably located at the outer side in the tire width direction than the center position 11 in the tire width direction of the bead portion 1 at the rim line position 10. This is because by arranging the carcass ply 4 close to the outer contour of the bead portion 1 in this manner, the case thickness of the bead portion can be reduced and weight reduction can be achieved. On the other hand, in the conventional tire shown in FIG. 10, the carcass ply passes through the approximate center of the bead thickness in the direction perpendicular to the carcass ply, but at the rim line position 110 than the tire width direction center position 111 of the bead portion 101. Since it is located outside in the width direction, the case thickness of the bead portion 101 is increased.

  The carcass ply 4 includes a main body portion 12 that extends in a toroidal shape between both bead portions and is sandwiched between the bead cores 2a and 2b, and a protruding portion 13 that is connected to the main body portion 12 and protrudes from the bead cores 2a and 2b. It is preferable. This is because the carcass ply 4 protrudes from the bead cores 2a and 2b, so that air remains in the bead cores 2a and 2b at the time of vulcanization molding, and this can be prevented from becoming a core of failure occurrence. Since the protruding portion 13 is vulcanized and bonded to the rubber material constituting the bead portion 1 and generates a force that resists pulling out of the carcass ply 4, the length of the protruding portion 13 should be 1 mm or more. From the viewpoint of enhancing the properties, it is preferable.

  3-5 has shown the tire width direction cross section of the other embodiment of this invention. The projecting portion 13 is formed by bending the end portion 14 of the carcass ply 4 so as to face the outer side in the tire radial direction, the projecting member 15 is provided on at least the inner surface of the projecting portion 13, and the projecting portion 13 is formed by the carcass ply. The rubber member 16 is preferably covered with a rubber member 16 having a 100% modulus equal to or greater than the 100% modulus of the coated rubber. If these structures are adopted, even if the protruding portion 13 of the carcass ply 4 moves toward the outer side in the tire width direction due to the influence of the tension T, this movement is prevented by the bead core 2a located on the outer side in the tire radial direction. Furthermore, when the protrusion part 13 contacts the bead core 2a, the bead core 2a is pressed toward the bead core 2b, the gap between the bead cores 2a and 2b is narrowed, and the holding force of the carcass ply 4 is increased. Combined with these actions, the locking force of the carcass ply is further increased, and the bead portion durability is improved. Note that these configurations can be used not only independently, but also in combination of two or three configurations.

  The larger the bending angle α of the protrusion 13 shown in FIG. Moreover, although the protrusion member 15 shown in FIG. 4 can be comprised with various materials, such as a metal, a plastics, glass, from a viewpoint of the heat resistance with respect to the high temperature at the time of vulcanization molding, and the durability at the time of long-term use, It is particularly preferable to use a metal. The metal that can be used is not particularly limited, and the protruding member can be composed of a pure metal such as iron, copper, and aluminum, and an alloy. From the viewpoint of adhesiveness to the rubber material surrounding the protruding member, brass is used. It is particularly preferable to use it. In this case, all the protruding members may be made of brass. However, since brass has a relatively high density, a core material is formed of a relatively low density metal such as aluminum, plastic or glass, and this surface is formed. It is preferable from a viewpoint of weight reduction to comprise a brass material or brass plating.

  It is assumed that the 100% modulus of the rubber member 16 shown in FIG. 5 is larger than that of the covered rubber of the carcass ply 4 because the rubber is higher than the covered rubber 4 of the carcass ply 4 when the same force is applied. This is because the deformation of the member 16 is reduced and the effect of locking the carcass ply 4 is enhanced by the rubber member 16 trying to maintain the original shape even when the tension T acts. The rubber member 16 is more preferably a rubber containing an adhesion promoter that promotes adhesion of the carcass ply 4 to the ply cord. Since a shearing force acts between the carcass ply 4 and the rubber member 16, cracks are likely to occur. However, if the rubber member 16 contains an adhesion promoter, the holding force of the carcass ply 4 by the rubber member 16 is increased. As a result, the locking effect and crack resistance of the carcass ply 4 are improved, and as a result, the durability of the bead portion 1 is further improved. The adhesion promoter can be appropriately selected according to the material of the ply cord, but when the ply cord is a steel cord, a metal salt of an organic acid, for example, a salt of cobalt, nickel, iron or the like is preferable. Particularly preferred are cobalt salts of organic acids. As a compounding quantity of cobalt salt, it is preferable to set it as 0.02-0.5 mass part as a cobalt element total compounding quantity with respect to 100 mass parts of rubber components.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . For example, although the description has been given taking an example in which three bent portions are provided for each bead core, the number of bent portions may be one, two, four or more. 6 and 7, the end portion 14 of the carcass ply 4 may face the inside in the tire radial direction. Further, the number of bent portions is not necessarily the same between the bead core 2a and the bead core 2b, and as shown in FIGS. 8 and 9, the number of bent portions of one bead core (bead core 2a in FIGS. 8 and 9) is the other bead core. The number may be one more than the number of bent portions of the bead core 2b in FIGS. Even in such a case, when the sandwiching surfaces 3a and 3b are brought into contact with each other, as long as the convex bent portion and the concave bent portion are engaged with each other except for the excessive bent portion, the complementary surfaces are in a complementary relationship. Consider it.

  Next, a pneumatic tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.

  The tire of the example is a 15 ° taper radial tire for trucks and buses having a tire size of 11R22.5, and has a bead portion structure as shown in FIG. Further, the bending width is 4 mm, 3 mm, and 2 mm in order from the outer side to the inner side in the tire width direction, the length of the protruding portion of the carcass ply is 5 mm, and the carcass ply is a tire at the bead portion at the rim line position. It is located on the outer side in the tire width direction than the center position in the width direction.

  For comparison, although the tire size and the carcass ply are the same as those of the example, the tire of the conventional example in which the bead structure has a pair of bead cores each having a bent portion as shown in FIG. A prototype was also made.

  Each of the test tires is mounted on a rim having a size of 8.25 × 22.5 to form a tire wheel, an air pressure of 700 kPa (relative pressure) is applied to the tire wheel, a running speed of 60 km / h, a tire load load of 29. While running on a drum tester for 100,000 km under the condition of 4 kN, all tires completed without any failure.

  FIG. 11 shows the case shape of the bead portion of each tire of the example and the conventional example. As is clear from FIG. 11, the tire of the example has a reduced case thickness at the bead portion compared to the conventional tire. Moreover, when the mass of each tire of an Example and a conventional example was measured, the tire of the Example was 3% lighter than the tire of the conventional example.

  As is apparent from the above description, the present invention can increase the degree of freedom of the carcass line and achieve significant weight reduction on the premise that the durability of the bead portion of the tire having the sandwich bead structure is maintained. It became.

1 is a tire width direction cross-sectional view of a bead portion of a typical pneumatic tire according to the present invention. (A) And (b) is a figure showing the outline shape of bead core 2a, 2b of FIG. 1, respectively. It is tire width direction sectional drawing of the bead part of the other pneumatic tire according to this invention. It is tire width direction sectional drawing of the bead part of the other pneumatic tire according to this invention. It is tire width direction sectional drawing of the bead part of the other pneumatic tire according to this invention. It is tire width direction sectional drawing of the bead part of the other pneumatic tire according to this invention. It is tire width direction sectional drawing of the bead part of the other pneumatic tire according to this invention. It is tire width direction sectional drawing of the bead part of the other pneumatic tire according to this invention. It is tire width direction sectional drawing of the bead part of the other pneumatic tire according to this invention. It is tire width direction sectional drawing of the bead part of the pneumatic tire of a prior art example. The case shape of the bead part of each tire of a prior art example and an example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2a, 2b Bead core 3a, 3b Nipping surface of bead core 4 Carcass ply 5a, 5b, 6a, 6b, 7a, 7b Bending part 8a, 8b Tire width direction outer end part of clamping surface 9a, 9b Tire width of clamping surface Rim line position 11 tire width direction center position of bead portion 12 carcass ply main body portion 13 carcass ply protrusion portion 14 carcass ply end portion 15 projecting member 16 rubber member

Claims (8)

In a pneumatic tire comprising a pair of bead portions, a carcass ply formed by covering a ply cord with rubber, and a pair of bead cores embedded in the bead portion and sandwiching the carcass ply by a pair of opposed surfaces,
In the tire width direction cross section,
One bead core is located on the outer side in the tire radial direction of the other bead core,
The surfaces sandwiching the carcass ply of each bead core each have at least one bent portion and are in a complementary relationship with each other,
The carcass ply extends in a toroidal shape between both bead portions and enters between the pair of bead cores from the outer side in the tire width direction.   2. The pneumatic tire according to claim 1, wherein the sandwiching surfaces of the bead cores have at least two bent portions, respectively, and the convex bent portions and the concave bent portions are alternately arranged.   The pneumatic tire according to claim 2, wherein the sandwiching surface of each bead core gradually decreases in bending width from the outer side in the tire width direction toward the inner side in the tire width direction.   The pneumatic tire according to any one of claims 1 to 3, wherein the carcass ply is positioned at an outer side in the tire width direction than a center position in the tire width direction of the bead portion at a rim line position.   The carcass ply includes a main body portion that extends in a toroidal shape between both bead portions and is sandwiched between each pair of bead cores, and a protruding portion that is connected to the main body portion and protrudes from the bead core. A pneumatic tire according to claim 1.   The pneumatic tire according to claim 5, wherein the protruding portion is bent so that an end portion of the carcass ply faces outward in the tire radial direction.   The pneumatic tire according to claim 5 or 6, wherein a protruding member is attached to at least an inner surface of the protruding portion.   The pneumatic tire according to any one of claims 5 to 7, wherein the protrusion is covered with a rubber member having a 100% modulus that is equal to or greater than 100% modulus of the covered rubber of the carcass ply.

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