JP2012188016A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a bead part by preventing CBU of a carcass cord.SOLUTION: In a pneumatic tire 1, a part around a bead core 5 of a bead part 4 is reinforced from a tread part 2 via a side wall part 3 by a carcass 6 including a carcass ply 6A folded back to the outer side from the inner side in the tire axial direction. The bead core 5 has a multi-stage multi-row winding structure in which a wire row S with one steel wire 10 being spirally wound while being deviated in the tire axial direction is superposed in a multi-stage manner in the tire radial direction. A winding end 10e of the steel wire 10 is located on the outermost side in the tire axial direction of the wire row S1 of the innermost layer in the tire radial direction.

Description

  The present invention relates to a pneumatic tire in which carcass cord breakage at a bead portion is prevented and durability of the bead portion is improved.

  FIG. 8 shows a general structure of a bead portion of a conventional heavy duty pneumatic tire. In the bead portion a, a bead core b formed by hexagonal cross-section by spirally winding a single steel wire w in multiple stages and multiple rows, and the bead core b is folded back from the inner side in the tire axial direction to the outer side. A carcass c including a carcass ply c1 is provided. And the winding end w1 of the steel wire w of the bead core b is provided at the innermost position in the tire axial direction of the innermost wire row in the tire radial direction (hereinafter sometimes simply referred to as “B point”). It was done.

  However, due to the tension of the carcass ply c1 due to internal pressure filling and the deformation of the carcass ply accompanying the bending deformation of the bead portion, the winding end w1 of the steel wire w of the bead core b at the point C where the carcass ply c1 is the innermost side in the tire axial direction. Cord breakage (hereinafter simply referred to as “CBU”) is likely to occur.

  The winding end w1 of the steel wire is a so-called free end, and no other steel wire exists on the inner side in the tire axial direction. Therefore, there is a problem that the winding end w1 moves to the vicinity of the point C due to the tension of the carcass ply generated during the vulcanization molding of the tire. Also in this case, the contact pressure between the sharp winding end w1 of the steel wire and the carcass ply c1 increases, and CBU is likely to occur.

Japanese Patent Laid-Open No. 08-57980 JP 2006-273119 A

  The present invention has been devised in view of the above-described problems, and is based on defining the arrangement position of the winding end of the steel wire forming the bead core, and suppresses the CBU of the carcass cord, The main purpose is to provide a pneumatic tire with improved durability.

  The invention according to claim 1 of the present invention is a pneumatic tire reinforced with a carcass including a carcass ply that is turned from the inner side to the outer side in the tire axial direction around the bead core of the bead part through the sidewall part from the tread part. The bead core has a multi-stage multi-row winding structure in which a wire row spirally wound with one steel wire shifted in the tire axial direction is stacked in multiple stages in the tire radial direction, and the steel wire The winding end is characterized by being positioned on the outermost side in the tire axial direction of the innermost layer wire row in the tire radial direction.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the bead core has a substantially hexagonal cross section.

  According to a third aspect of the present invention, the bead portion includes a wrapping material that covers an outer peripheral surface of the bead core between the bead core and the carcass ply, and the wrapping material is a parallel body of a plurality of organic fiber cords. The pneumatic tire according to claim 1 or 2, comprising at least one ply covered with a topping rubber.

  In the invention according to claim 4, the organic fiber cord of the wrapping material has a thickness of 1000 to 4200 dtex, a cord interval of 0.3 to 2.0 mm, and an angle α1 with respect to the tire circumferential direction in the cord longitudinal direction of 20 to 20 mm. The pneumatic tire according to claim 3, which is 70 degrees.

  The invention according to claim 5 is the heavy duty pneumatic tire according to claim 3 or 4, wherein the topping rubber has a rubber hardness Ht of 70 to 90 degrees.

  According to a sixth aspect of the present invention, the wrapping material comprises two plies wound together, and the organic fiber cord of each ply is inclined in the same direction with respect to the tire circumferential direction. A pneumatic tire according to any one of the above.

  According to a seventh aspect of the present invention, the wrapping material comprises two plies wound together, and the organic fiber cords of the respective plies are inclined in the opposite direction to the tire circumferential direction so as to cross each other. A pneumatic tire according to any one of claims 3 to 5.

  In the pneumatic tire of the present invention, the bead core has a multi-stage multi-row winding structure in which a wire row spirally wound by shifting one steel wire in the tire axial direction is stacked in multiple stages in the tire radial direction. The winding end of the wire is provided on the outermost side in the tire axial direction of the innermost layer wire row in the tire radial direction. In general, when the bead portion is deformed, the carcass ply is also deformed accordingly, but in the radially inner region of the outermost position in the tire axial direction of the wire array of the innermost layer of the bead core in the tire radial direction, the carcass ply has the rim and the bead core. It is strongly sandwiched between and hardly deformed. Therefore, since the relative displacement between the winding start end of the steel wire and the carcass ply does not occur, the generation of CBU can be suppressed. Moreover, in this invention, since the steel wire wound next is located inside the tire axial direction inner side of the winding end of a steel wire, the movement to the tire axial direction inner side of a winding end can also be prevented. Therefore, in the pneumatic tire of the present invention, the occurrence of CBU is suppressed over a long period of time, and the durability of the bead portion is improved.

It is sectional drawing of the right half of the pneumatic tire of one Embodiment of this invention. It is sectional drawing which expands and shows the bead part. It is sectional drawing which expands and shows a bead part further. It is the X section enlarged view of FIG. It is a top view explaining the cord arrangement of the wrapping material of this embodiment. It is a top view explaining the code | cord | chord arrangement | sequence of the wrapping material of other embodiment. It is sectional drawing of the holder which spirally winds steel wire and shape | molds a bead core. It is sectional drawing of the bead part of the conventional pneumatic tire.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 to 3, a pneumatic tire (hereinafter, simply referred to as “tire” in some cases) 1 according to this embodiment includes a bead core 5 of a bead portion 4 that extends from a tread portion 2 to a sidewall portion 3. , And a belt layer 7 disposed on the outer side in the radial direction of the carcass 6 and inside the tread portion 2. In this embodiment, a heavy load is shown.

  The carcass 6 includes a main body part 6a straddling a pair of bead cores 5 and 5 in a toroidal manner, and a folded part 6b which is continuous from both sides of the main body part 6a and is folded around the bead core 5 from the inner side to the outer side in the tire axial direction. And at least one carcass ply 6A in this embodiment. As shown in FIG. 3, the carcass ply 6A is made of, for example, steel and arranged at an angle of, for example, 75 to 90 ° (90 ° in the present embodiment) with respect to the tire equator C direction, And a topping rubber 6d coated on both sides of the carcass cord 6c array.

  In the present embodiment, the belt layer 7 includes a total of four belt plies 7A to 7D arranged inside and outside in the tire radial direction. For example, the belt ply 7B having the largest tire axial width is formed from the inside in the tire radial direction. It is arranged in the second layer. Each of the belt plies 7A to 7D includes a highly elastic belt cord such as a steel cord inclined at an angle of 15 to 55 ° with respect to the tire equator C. The belt plies 7A to 7D are overlapped with at least one portion where the belt cords intersect each other. As a result, the belt layer 7 is particularly suitable as a structure for a small truck having a large load because the carcass 6 is hooked over substantially the entire width of the tread portion 2 and the rigidity of the tread portion 2 is increased.

  A bead apex rubber 8 for bead reinforcement that extends from the bead core 5 toward the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A.

  As shown in FIG. 2 in an enlarged manner, the bead apex rubber 8 of the present embodiment is formed of, for example, an inner apex portion 8a formed of a hard rubber layer in the radial direction and a softer rubber than the inner apex portion 8a. The outer apex 8b is formed radially outward. Such a bead apex rubber 8 is effective in relieving the shear stress acting on the turn-up portion 6b of the carcass ply 6A while ensuring sufficient bending rigidity when the bead portion 4 is deformed, thereby effectively preventing damage such as separation. To prevent.

  The bead portion 4 is provided with a bead reinforcing layer 9. The bead reinforcing layer 9 is made of, for example, a steel cord ply. The steel cords of the bead reinforcing layer 9 are preferably arranged at an angle of 10 to 60 ° with respect to the tire circumferential direction. Further, the steel cord ply preferably includes an inner piece 9i extending along an inner side surface in the tire axial direction of the main body portion 6a, and an axial direction of the folded portion 6b in the bottom piece 9a passing through the inner side in the tire radial direction of the bead core 5. It is formed in a U-shaped cross section provided with an outer piece 9o extending along the outer side surface. Such a bead reinforcing layer 9 increases the bending rigidity of the bead portion 4.

  The bead portion 4 is provided with a clinch rubber 19. The clinch rubber 19 rises radially outward from the outer end portion in the tire axial direction and forms a bead base surface 4s that is the inner surface in the tire radial direction of the bead portion 4 and contacts at least the rim flange Rj of the rim R. In the region, it includes a rising portion 19b that forms the outer surface of the bead. Such a clinch rubber 19 prevents rim displacement of the bead portion 4 and contact wear between the carcass 6 and the rim.

  The bead core 5 includes a core inner peripheral surface 5L extending along the rim sheet Rs of the rim R and a core outer periphery parallel to the core inner peripheral surface and radially outward of the core inner peripheral surface 5L in a tire meridional section including a tire axis. It is comprised by the substantially hexagonal shape of cross-sectional landscape including the surface 5U. Such a bead core 5 exhibits a stable fitting force with respect to the rim sheet Rs, and helps to increase the torsional rigidity around the center of the cross section of the bead core 5.

  Further, the bead core 5 has a multi-stage multi-row winding structure in which a wire row S obtained by spirally winding a single steel wire 10 in the tire axial direction is stacked in multiple stages on the outer side in the tire radial direction, in this embodiment six stages. Have.

  The winding end 10e of the steel wire of the present invention (the winding start end 10s that is the start of winding) is the outermost position in the tire axial direction of the wire array S1 of the innermost layer in the tire radial direction (hereinafter referred to as “point A”) Is provided). Then, without cutting the steel wire 10, a six-stage wire row is formed while alternately changing the direction of the spiral, and the winding end 10t is the tire shaft of the outermost wire row Sg in the tire radial direction. It is provided at the outermost position in the direction (hereinafter sometimes referred to as “F point”) or the innermost position in the tire axial direction (hereinafter also referred to as “point E”). In the present embodiment, the winding end 10t is provided at the point F.

  In general, when the bead portion is deformed, the carcass ply 6A (carcass cord 6c) is deformed accordingly, but in the radially inner region of the outermost position in the tire axial direction of the wire row of the innermost layer of the bead core in the tire radial direction, The carcass ply 6A is strongly sandwiched between the rim R and the bead core 5 and hardly deforms. Therefore, since the relative displacement between the winding start end 10s of the steel wire 10 and the carcass ply 6A does not occur, the generation of CBU can be suppressed.

  In the present invention, the steel wire wound next is positioned inside the winding start end 10 s of the steel wire 10 in the tire axial direction. For this reason, even if tension due to tire vulcanization or inflation acts on the outer side in the tire radial direction of the carcass ply 6A, the winding start end 10s is prevented from moving inward in the tire axial direction (for example, the C point side). it can. Therefore, in the pneumatic tire of the present invention, the occurrence of CBU is suppressed over a long period of time, and the durability of the bead portion is improved.

  FIG. 4 shows an enlarged view of a portion X in FIG. The bead core 5 of this embodiment is formed by attaching an unvulcanized bead coating rubber 14 to the steel wire 10 in advance and spirally winding it. For this reason, the bead coating rubber 14 is arranged in the gap between the steel wires 10. Such a bead coating rubber 14 serves to prevent movement of each steel wire 10 and suppress CBU.

  As shown in FIGS. 3 to 5, in the present embodiment, a wrapping material 11 that covers the outer peripheral surface of the bead core 5 is provided between the bead core 5 and the carcass ply 6A.

  The wrapping material 11 is composed of at least one ply in which a parallel body of a plurality of organic fiber cords 12 is covered with a topping rubber 13, in this embodiment, two plies 11A and 11B. Such a wrapping material 11 surrounds the outer peripheral surface of the bead core 5 to prevent deformation thereof, and ensures a distance between the steel wire winding end 10e and the carcass ply 6A of the carcass ply 6A. Fretting can be prevented. Therefore, in such an embodiment, generation of CBU is further suppressed.

  For the organic fiber cord 12 of the wrapping material 11, for example, a fiber such as nylon, rayon, polyester, aromatic polyamide, or vinylon is employed. Further, the organic fiber cord 12 is not particularly limited, but has a thickness D1 of 1000 to 4200 dtex, a cord interval W1 of 0.3 to 2.0 mm, and an angle α1 with respect to the tire circumferential direction in the cord longitudinal direction. The thing of 20-70 degree | times is preferable.

  That is, when the thickness D1 (shown in FIG. 5) of the organic fiber cord 12 is reduced, the fretting prevention effect is lowered and the strength as the wrapping material 11 may be difficult to be secured. On the contrary, when the thickness D1 is increased, it tends to be difficult to surround the outer peripheral surface of the bead core 5 with the wrapping material 11. From such a viewpoint, the thickness D1 of the organic fiber cord 12 is more preferably 1400 dtex or more, and more preferably 3760 dtex or less. In addition, this thickness D1 means the total fineness. From the same viewpoint, the cord interval W1 (shown in FIG. 5) of the organic fiber cord 12 is more preferably 0.4 mm or more, and more preferably 1.5 mm or less.

  Further, when the angle α1 (shown in FIG. 5) of the organic fiber cord 12 of the wrapping material 11 with respect to the tire circumferential direction in the cord longitudinal direction becomes small, the organic fiber cord 12 is easily sunk between the steel wires 10 and 10, and the carcass ply 6A and the winding end 10e may be brought close to each other. On the contrary, when the angle α1 is increased, the arrangement angle between the organic fiber cord 12 and the carcass cord 6c is approximated, and the organic fiber cord 12 is likely to be fitted into the carcass ply 6A, and the winding end of the carcass cord 6c and the steel wire is made. There is a tendency that a sufficient distance from 10e is difficult to be secured. From such a viewpoint, the angle α1 is more preferably 30 degrees or more, and more preferably 60 degrees or less.

  The rubber hardness Ht of the topping rubber 13 constituting the wrapping material 11 is preferably 70 degrees or more, more preferably 73 degrees or more, and preferably 90 degrees or less, more preferably 87 degrees or less. If the rubber hardness Ht is small, the ability to fix the winding end 10e of the steel wire may be reduced. On the other hand, if the rubber hardness Ht is large, rubber scorch occurs during kneading of the topping rubber 13, and the quality or strength of the wrapping material 11 may be lowered. The rubber hardness is a durometer A hardness measured with a durometer type A at a temperature of 23 ° C. based on JIS-K6253.

  As shown in FIG. 4, in the pneumatic tire 1 of the present embodiment, the shortest distance L1 between the steel wire 10 on the innermost side in the tire axial direction of the bead core 5 at the point C or the point B and the carcass cord 6c is set. The thickness is preferably 0.4 mm or more, more preferably 0.6 mm or more, and preferably 3.0 mm or less, more preferably 2.5 mm or less. If the shortest distance L1 is large, the carcass cord 6c and the bead core 5 may be peeled off due to heat generated during traveling, and the durability of the bead portion may be deteriorated. Conversely, if the shortest distance L1 is small, the steel wire Wrapping end 10e and carcass ply 6A may come into contact with each other, and CBU may be easily generated.

  Since the wrapping material 11 of this embodiment is composed of two plies 11A and 11B, the shortest distance L1 can be easily secured within the specified range. At this time, as shown in FIG. 5, the organic fiber cords 12 a and 12 b of the two plies 11 </ b> A and 11 </ b> B are arranged in an inclined direction opposite to the tire circumferential direction so as to intersect each other. desirable. As a result, fretting between the carcass ply 6A and the steel wire 10 can be prevented more reliably, and CBU can be more effectively suppressed. The organic fiber cords 12a and 12b of the two plies 11A and 11B are more preferably arranged at the same angle with respect to the tire circumferential direction. Thereby, the effect which suppresses the above-mentioned CBU is further improved.

  6, the organic fiber cords 12a and 12b of the two plies 11A and 11B of the wrapping material 11 may be inclined in the same direction with respect to the tire circumferential direction.

  The bead core 5 as described above is formed using a holder 20 as shown in FIG. 7, for example. The holder 20 is formed in a disk shape provided with a forming groove 21 extending in the circumferential direction for winding the steel wire 10. The groove 21 has a groove bottom surface 21a that forms a wire row in the innermost layer in the tire radial direction and has a diameter that increases from one side to the other side, and an inclination angle β thereof is substantially equal to the gradient of the rim seat Rs and is about 15 degrees. It is. Further, the groove bottom surface 21 a is provided with a concave groove g for positioning the winding start end 10 s of the steel wire 10 to prevent the deviation at the end on the diameter expansion side. Such a holder 20 can prevent the initial displacement of the winding start end 10 s of the steel wire 10 and can efficiently form the bead core used in the present invention without misalignment.

  As mentioned above, although the especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A heavy-duty tire of size 11R22.5 having the basic structure of FIGS. 1 to 4 was prototyped based on the specifications in Table 1, and the following drum running test was performed. The specifications other than those in Table 1 are substantially the same.

<Drum durability test>
Each sample tire was mounted on a rim of 8.25 × 20, the organic fiber cord of the wrapping material was nylon, and a drum having a diameter of 1700 mm was run at a speed of 20 km / h with a slip angle of 0 ° and a camber angle of 0 °. Then, the traveling time until the fretting occurred between the steel wire and the carcass cord was compared. The evaluation was expressed as an index with the traveling time of Comparative Example 1 as 100. The larger the value, the better.
Load: 58.84kN
Internal pressure: 1000kPa
The test results are shown in Table 1.

  As a result of the test, it can be understood that in the example, the running time is longer than in the comparative example, and the durability of the bead portion is improved. Further, when the thickness of the organic fiber cord of the wrapping material is increased or the interval between the cords is decreased, the running time becomes longer, but there is a problem that it takes time to manufacture. Furthermore, the same test was performed on the rectangular bead core, and the same tendency as the test result was shown.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 10 Steel wire 10 Steel wire winding end S Wire row S1 Innermost wire row in the tire radial direction

The invention according to claim 5, rubber hardness Ht of the topping rubber is empty pneumatic tire according to claim 3 or 4 which is 70 to 90 degrees.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 10 Steel wire 10 e Winding end S of steel wire S Wire row S1 The innermost wire row in the tire radial direction

Claims (7)

A pneumatic tire reinforced with a carcass including a carcass ply folded from the inner side to the outer side in the tire axial direction around the bead core of the bead part from the tread part through the sidewall part,
The bead core has a multi-stage multi-row winding structure in which a wire row spirally wound by shifting one steel wire in the tire axial direction is stacked in multiple stages in the tire radial direction,
Moreover, the pneumatic tire is characterized in that a winding end of the steel wire is located on the outermost side in the tire axial direction of the innermost wire row in the tire radial direction.   The pneumatic tire according to claim 1, wherein the bead core has a substantially hexagonal cross section. The bead portion includes a wrapping material that covers an outer peripheral surface of the bead core between the bead core and the carcass ply,
3. The pneumatic tire according to claim 1, wherein the wrapping material includes at least one ply in which a parallel body of a plurality of organic fiber cords is covered with a topping rubber.   The organic fiber cord of the wrapping material has a thickness of 1000 to 4200 dtex, a cord interval of 0.3 to 2.0 mm, and an angle α1 with respect to the tire circumferential direction of the cord longitudinal direction of 20 to 70 degrees. Pneumatic tire.   The heavy duty pneumatic tire according to claim 3 or 4, wherein the topping rubber has a rubber hardness Ht of 70 to 90 degrees. The wrapping material consists of two plies rolled up,
The pneumatic tire according to any one of claims 3 to 5, wherein the organic fiber cord of each ply is inclined in the same direction with respect to the tire circumferential direction. The wrapping material consists of two plies rolled up,
The pneumatic tire according to any one of claims 3 to 5, wherein the organic fiber cord of each ply is inclined in a direction opposite to the tire circumferential direction so as to cross each other.

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