JP2012126298A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which improves durability of a bead part by improving a winding and piling method of the bead wire.SOLUTION: The pneumatic tire 1 contains: a carcass 6 comprising a carcass ply 6A which extends striding over between a pair of bead parts 4 and 4 in a toroidal shape; and a bead core 5 which includes an inside core 11 and an outside core 12 arranged at inside and outside of a tire axial direction of an inner end 6e of the tire radial direction inside of the carcass ply 6A. The inner core 11 and outside core 12 are formed by winding and piling bead wires 13 and 14, respectively, in n layers (n is an integer ≥3) in whorl around the tire rotational axis. In the inner core 11 and outside core 12, both the winding starting end and the winding terminals of the bead wires 13 and 14 are located in the outermost layers 11a and 12a of the tire radial directions of the core 11 and 12, respectively.

Description

  The present invention relates to a method for manufacturing a pneumatic tire in which a bead wire winding method is improved to improve the durability of a bead portion.

  In recent years, as shown in FIG. 5, a manufacturing method (core method) of a pneumatic tire 1 using a core N having an outer surface P approximated to a tire inner surface shape at the time of internal pressure filling has been proposed (the following method). Patent Document 1). In this type of manufacturing method, the inner cover 9, the carcass ply 6A, the bead wire 10, the belt layer 7, the tread rubber 2G, the sidewall rubber 3G, and the like are sequentially attached to the outside of the core N, thereby forming the green cover 1a. In general, the raw cover 1a is vulcanized together with the core N. This method has an advantage that the uniformity of the pneumatic tire is improved because the stretch acting on the carcass and the belt during vulcanization can be kept small.

JP 2006-160236 A

  By the way, in the above-described core method, both ends of the carcass ply 6A cannot be folded back. For this reason, the bead core 5 formed by the core method employs a structure in which the bead wire 10 is spirally wound from the inner side to the outer side in the tire radial direction and arranged on both sides of the carcass ply 6A to sandwich the carcass ply 6A. ing. In such a bead core 5, as shown in FIG. 6A, the end 10 e of the bead wire 10 is the most in the tire radial direction of the bead core 5, which tends to generate a large stress due to the tensile force of the carcass ply when the tire rolls. Arranged in the inner layer 5a. The pneumatic tire 1 having such a bead core has a problem that due to stress concentration on the end portion 10e of the bead wire 10, rubber peeling occurs at the end portion 10e, which grows and damages the bead portion 4. .

  The present invention has been devised in view of the above problems, and in a core construction method using a core, a pneumatic tire in which the bead wire winding method is improved to improve the durability of the bead portion. The main purpose is to provide a manufacturing method.

  According to the first aspect of the present invention, a carcass formed of a carcass ply extending across a toroidal shape between a pair of bead portions, and an inner end portion of the carcass ply at an inner end in a tire radial direction inside and outside in the tire axial direction. A pneumatic tire including a bead core composed of an inner core and an outer core, wherein the inner core and the outer core each have one bead wire arranged around the tire rotation axis and spirally in n layers (n is The inner core and the outer core are both formed by winding the bead wire at the winding start end and winding end at the outermost layer in the tire radial direction of each core. It is a pneumatic tire.

  Further, in the invention according to claim 2, each of the inner core and the outer core is a first portion in which the bead wire is wound in a spiral shape from the winding start end to the innermost layer in a direction of decreasing in diameter toward the inner side in the tire radial direction. 2. The pneumatic tire according to claim 1, wherein the bead wire includes a second portion wound in a spiral shape from the innermost layer to a winding end of the outermost layer in a direction that expands radially outward from the tire.

  According to a third aspect of the present invention, in each of the inner core and the outer core, the first portion bead wire and the second portion bead wire have a vertically aligned portion in which the bead wires of the second portion are vertically aligned in the tire radial direction. The pneumatic tire described.

  According to a fourth aspect of the present invention, each of the inner core and the outer core has a side-by-side portion in which the bead wire of the first portion and the bead wire of the second portion are side-by-side in the tire axial direction. The pneumatic tire described.

  According to a fifth aspect of the present invention, in the side-by-side portions of the inner core and the outer core, the angles of the side-by-side portions adjacent to the tire circumferential direction of the respective cores with respect to the tire circumferential direction are formed at equal angles. The pneumatic tire described.

  The pneumatic tire according to the present invention includes a carcass made of a carcass ply extending across a toroidal shape between a pair of bead parts, and an inner side arranged inside and outside in the tire axial direction of an inner end of the carcass ply in the tire radial direction. And a bead core composed of an outer core. The inner core and the outer core are each formed by winding one bead wire around the tire rotation axis and spirally in n layers (n is an integer of 3 or more), and the inner core and the outer core are The winding start end and winding end of the bead wire are both located in the outermost layer in the tire radial direction of each core.

  Thus, in the pneumatic tire of the present invention, since both winding ends of the bead wire are disposed on the outermost side of the bead core in the tire radial direction, a large stress concentration on the end portion of the bead wire can be suppressed. Is prevented, and the durability of the bead portion is improved.

1 is a right half sectional view of a pneumatic tire according to the present invention. It is a side view of the inner core of a bead part. (A) is the 1st part of the inner core of FIG. 2, (b) is a side view of the 2nd part. (A) is AA sectional drawing of FIG. 2 explaining a vertical alignment part, (b) is BB sectional drawing of FIG. 2 explaining a horizontal alignment part. It is the right half surface sectional drawing of the raw cover obtained by a core construction method, and a core. It is a side view of the bead part explaining the conventional bead core.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of the right half of a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. In addition, a passenger car is provided that includes an inner liner 9 made of rubber excellent in air impermeability disposed inside the carcass 6 and on the tire cavity surface M.

  The pneumatic tire 1 in FIG. 1 shows a normal state in which a normal rim (not shown) is assembled with a rim and filled with a normal internal pressure and is in an unloaded state.

  Here, 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, a standard rim for JATMA, “Design Rim” for TRA, For ETRTO, use “Measuring Rim”. In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure for JATMA and the table “TIRE LOAD LIMITS AT for TRA” Maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars.

  The carcass 6 is composed of at least one carcass ply 6A having a carcass cord extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. In the carcass ply 6A, carcass cords made of, for example, organic fibers are arranged at an angle of, for example, 75 to 90 ° with respect to the tire equator C direction. The carcass ply 6 </ b> A of the present embodiment extends between the pair of bead portions 4, 4 in a toroidal shape, and inner end portions 6 e on the inner sides in the tire radial direction on both sides thereof are not folded back by the bead core 5. It ends with.

  The belt layer 7 is composed of at least two belt plies 7A and 7B, in the present embodiment, in the tire radial direction, and in the outer two. Each of the belt plies 7A and 7B has a highly elastic belt cord such as a steel cord inclined at an angle of 15 to 40 ° with respect to the tire equator C. The belt plies 7A and 7B are overlapped so that the belt cords cross each other.

  In this embodiment, the bead core 5 includes an inner core 11 disposed on the inner side in the tire axial direction of the inner end 6e on the inner side in the tire radial direction of the carcass ply 6A, and an outer side in the tire axial direction of the inner end 6e. And an outer core 12 disposed. The inner end portion 6e of the carcass ply 6A is a portion extending in the bead portion 4 including the inner end of the carcass ply 6A.

  In the pneumatic tire 1 of the present invention, as the inner core 13 is representatively shown in FIG. 2, the inner core 11 and the outer core 12 are each composed of one bead wire (the bead wire 13 and the outer core forming the inner core 11). The bead wire 14) forming 12 is wound around the tire rotation axis and spirally wound around n layers (n is an integer of 3 or more, and in this embodiment, it is formed in 5 layers). Has been. Further, in the inner core 11, the winding start end 13a and winding end 13b of the bead wire 13 are located in the outermost layer 11a in the tire radial direction of the inner core 11, and in this embodiment, both winding ends 13a and 13b are They are arranged facing each other with a small gap s filled with rubber. Similarly, the outer core 12 has a winding start end (not shown) and a winding end (not shown) of the bead wire 14 positioned on the outermost layer 12a of the outer core 12 in the tire radial direction, and both windings. The tapping ends are arranged facing each other with a small gap.

  In such a pneumatic tire 1, both the winding ends 13a and 13b of the bead wire 13 are arranged on the innermost layer 11b in the tire radial direction of the bead core 5 which receives a large stress by the tensile force of the carcass ply when the tire rolls. There is nothing to do. Therefore, the pneumatic tire 1 of the present invention suppresses stress concentration occurring at the winding ends 13a and 13b, prevents rubber peeling of the winding ends 13a and 13b, and improves the durability of the bead portion 4. . In the present embodiment, the outer core 12 is formed with the same structure and the same shape as the inner core 11, and therefore, hereinafter, the same part as the inner core 11 will be described in a simplified manner.

  Further, as shown in FIG. 3A, the inner core 11 of the present embodiment is spirally formed to the innermost layer 11b in a direction in which the bead wire 13 decreases in diameter from the winding start end 13a toward the inner side in the tire radial direction. As shown in FIG. 3 (b), the wound first portion 16 and the bead wire 13 spirally extend from the innermost layer 11b to the winding end 13b of the outermost layer 11a in the direction of increasing the diameter outward in the tire radial direction. And the second portion 17 wound around the wire. The first portion 16 and the second portion 17 can maintain a high tire uniformity because the bead wires 13 do not overlap each other in the tire axial direction. Similarly, the outer core 12 is also formed of a first portion and a second portion.

  The first portion 16 of the inner core 11 includes an equal-diameter portion 18a in which the bead wire 13 is curved with a substantially constant curvature radius, and a reduced-diameter portion 18b that is connected to the equal-diameter portion 18a and gradually reduces the curvature radius. Formed. In the present embodiment, the angle θ1 with respect to the tire circumferential direction between the reduced diameter portions 18 and 18 adjacent to each other in the tire circumferential direction is substantially equal. The second portion 17 of the present embodiment includes an equal-diameter portion 19a in which the bead wire 13 is curved with a substantially constant curvature radius, and a diameter-expanded portion that is continuous with the constant-diameter portion 19a and gradually increases the curvature radius. 19b, and an angle θ2 with respect to the tire circumferential direction between the adjacent enlarged diameter portions 19b and 19b is arranged at substantially equal angles. The first portion 16 and the second portion 17 are useful for maintaining a high tire uniformity. In the present embodiment, the angles θ1 and θ2 are formed at 90 degrees. The “substantially equiangular” includes not only the case where the angles θ (θ1, θ2) are formed at equal angles, but also the case where each angle θ is in the range of θ ± 10 degrees. .

  Further, as shown in FIG. 2 and FIG. 4A which is an AA cross section thereof, the inner core 11 is composed of the bead wire 13 of the first portion 16 and the bead wire 13 of the second portion 17 as a tire. For example, it has a vertically aligned portion 20 which is closely aligned in the radial direction. Such a vertically aligned portion 20 is useful for maintaining high tire uniformity, particularly lateral force variation (LFV). As shown in FIG. 2, in the present embodiment, the vertically aligned portion 20 forms a main portion of the inner core 11.

  Further, as shown in FIG. 2 and FIG. 4B which is a BB cross section thereof, the inner core 11 of the present embodiment includes a bead wire 13 of the first portion 16 and a bead wire 13 of the second portion 17. Have side-by-side portions 21 that are side-by-side in the tire axial direction. The side-by-side portion 21 of the present embodiment is formed by intersecting the reduced diameter portion 18b and the enlarged diameter portion 19b. Such a side-by-side portion 21 is necessary for positioning the winding ends 13a and 13b on the outermost layer 11a when each core is formed by a single bead wire 13.

  Further, as shown in FIG. 2, in the present embodiment, the side-by-side portion 21 is formed such that the angle θ3 with respect to the tire circumferential direction of the side-by-side portions 21 and 21 adjacent in the tire circumferential direction is substantially equal. Is desirable. By arranging the side-by-side portions 21 at an equal pitch in this way, it is possible to minimize a decrease in tire uniformity due to the provision of the side-by-side portions 21. The “substantially equiangular” includes not only the case where the angle θ3 is formed at an equal angle, but also the case where each angle θ3 is in the range of θ3 ± 10 degrees. Such vertically aligned portions and horizontally aligned portions are also provided in the outer core 12.

  As shown in FIG. 1, the bead portion 4 of the present embodiment includes a hard portion in a region in contact with a rim (not shown) on the inner side in the tire radial direction of the bead core 5 and the outer side in the tire axial direction of the outer core 12. A chafer rubber 4g made of the above rubber is arranged. Further, inner and outer apexes 8i and 8o are provided so as to taper from the inner side in the tire axial direction of the inner core 11 and the outer side in the tire axial direction of the outer core 12 to the outer side in the tire radial direction. Such chafer rubber 4g and apex 8i, 8o are useful for increasing the bending rigidity of the bead portion 4 and improving the steering stability.

  The pneumatic tire 1 configured as described above is manufactured by vulcanizing a raw cover 1a as shown in FIG.

  Next, the manufacturing method of the pneumatic tire 1 of this invention is demonstrated. The pneumatic tire 1 of the present embodiment is manufactured using, for example, a core N as shown in FIG.

  The core N of the present embodiment includes, for example, a pair of a three-dimensional outer surface P that approximates the inner shape of a tire in a 5% internal pressure state and a bead side end portion of the outer surface P and that protrudes outward in the tire axial direction. And a flange surface F. The inner shape of the tire here is the inner shape of the tire 1 to be manufactured. The “5% internal pressure state” refers to a state in which the internal pressure is reduced from the normal state to an internal pressure of 5% of the normal internal pressure. The cross-sectional shape of the tire in the 5% internal pressure state approximates the cross-sectional shape of the tire in the vulcanization mold. However, the outer surface P of the core N is not necessarily limited to such a shape.

  In the present embodiment, first, a base portion 4ga of the chafer rubber 4g and the inner liner 9 are attached to the outer surface P of the core N, and then the bead portion 4 between the base portion 4ga and the inner liner 9 is bonded. The inner apex 8i is attached to the outer side in the tire axial direction.

  The base portion 4ga of the chafer rubber 4g has, for example, an L-shaped cross section, is placed on the flange surface F of the core N, and is wound around in a ring shape.

  Further, the inner liner 9 is formed on a three-dimensional curved surface by, for example, winding an unvulcanized and ribbon-shaped rubber strip (not shown) around the outer surface P of the core N along the circumferential direction thereof. It is formed. For example, the rubber strip preferably has a width W of about 5 to 35 mm and a thickness t of about 0.5 to 2.0 mm. In the present embodiment, the entire inner surface 9 of the core N is covered with the inner liner 9 and the base 4ga.

  The inner apex 8i is disposed on the outer side of the tire radius of the base portion 4ga placed on the flange surface F and on the inner side portion of the inner core 11 in the tire axial direction. Such an apex 8 i prevents the bead wire 13 of the inner core 11 from damaging the inner liner 9.

  Next, in this embodiment, the inner side process which forms the inner core 11 in the tire axial direction outer side of the inner apex 8i is performed. This process has a first step of forming the first portion 16 and a second step of forming the second portion 17.

  The first step includes a step of attaching the winding start end 13a of the bead wire 13 to a predetermined position outside the flange surface F in the tire radial direction. The outer peripheral surface of the bead wire 13 is previously coated with unvulcanized rubber. In this step, since the inner apex 8i is also an unvulcanized rubber, the bead wire 13 can be easily attached to the inner apex 8i.

  For example, by rotating the core N around the tire rotation axis, the bead wire 13 continuously supplied from a bead wire 13 supply device (not shown) is wound spirally inward in the tire radial direction. At this time, for example, it is desirable to wind the bead wire 13 while pressing it on the inner apex 8i by a bead wire pressing device such as a roller (not shown). As shown in FIG. 3A, the first portion 16 of the present embodiment is configured such that the bead wire 13 is, for example, 90 degrees, 270 degrees, 540 degrees, and 720 degrees in the tire circumferential direction from the winding start end 13a. The reduced diameter portion 18b is disposed at the moved position.

  In the present embodiment, the bead wire 13 is wound about 2.5 times, whereby the first portion 16 is formed, and the second step is subsequently started. Also in this second step, the second portion 17 is formed by winding the bead wire 13 about 2.5 times. In the second portion 17 of the present embodiment, as shown in FIG. 3B, the bead wire 13 is, for example, 180 degrees, 360 degrees, 450 degrees, and 630 in the tire circumferential direction from the terminal portion 16 a of the first portion 16. The diameter-expanded portion 19b is disposed at the position that has been moved. Thereby, the side-by-side portion 21 where the reduced diameter portion 18b and the enlarged diameter portion 19b intersect is formed. In addition, the arrangement | positioning position of the reduced diameter part 18b and the enlarged diameter part 19b is not limited to the above positions.

  Next, a carcass sticking step is performed in which the inner end portion 6e of the carcass ply 6A is stuck to the outer side of the inner core 11 in the tire axial direction. In the step, for example, a plurality of strip-like ply pieces 16 that are longer in the radial direction of the tire than the length in the tire circumferential direction are connected to the outer side in the tire axial direction of the inner core 11 and in the tire circumferential direction. The original carcass ply 6A is formed with high accuracy.

  Next, after the carcass 6 is formed, an outer step of forming the outer core 12 is performed. This process also includes a first step for forming the first part and a second step for forming the second part, as in the inner process.

  In this way, the bead wire winding start end 13a and the winding end end 13b of the inner core 11 are positioned on the outermost layer 11a in the tire radial direction of the inner core 11, and the bead wire winding start end and winding of the outer core 12 are also performed. The end is located in the outermost layer 12a of the outer core 12 in the tire radial direction.

  Then, as shown in FIG. 5, the outer apex 8o, the base portion 4ga of the clinch rubber 4g and the sub-portion 4gb forming the bead outer surface, the belt layer 7, the side wall rubber 3G, the tread rubber 2G, and the like are attached. Attached. In this way, the raw cover 1a is formed on the outer surface P of the core N.

  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.

  In order to confirm the effect of the present invention, the tire having the bead core of the present invention using the core shown in FIG. 5 and the conventional tire having the bead core shown in FIGS. 6A and 6B are vulcanized. Pneumatic tires were then prototyped and tested for breaking water pressure and uniformity. The main common specifications are as follows.

Number of carcass plies: 1 Carcass cord material: Polyester Carcass cord angle: 88 ° (against tire equator)
Number of belt plies: 2 Belt cord material: Steel Belt cord angle: + 28 °, -28 ° (to tire equator)
Bead wire rubber hardness: 80 degrees Bead wire wire material: Steel Tire size: 195 / 65R15

<Destruction water pressure>
Each sample tire was assembled with a rim of 6.0 JJ × 15, filled with water from the valve into the tire lumen, and measured the breaking water pressure when the bead core broke five times, and the average value of the breaking water pressure was determined. . The results were evaluated using an index with Conventional Example 1 being 100. Larger numbers are better.

<Uniformity>
Using a tire uniformity tester, RFV was measured in accordance with JASO C607: 2000 “Automatic tire uniformity test method”.
The tire measurement conditions are as follows.
Tire rotation speed: 60rpm
Air pressure: 200kPa
Longitudinal load: 4.63kN
The result was an average value of five tires, and was evaluated by an index with the reciprocal number of Conventional Example 1 being 100. Larger numbers are better. The test results are shown in Table 1.

  As shown in Table 1, it can be understood that the tires of the examples are superior in breaking water pressure and uniformity as compared with the conventional examples.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 5 Bead core 4 Bead part 6 Carcass 6A Carcass ply 11 Inner core 12 Outer core 13 Inner core bead wire 13a Winding start end 13b Winding end 14 Outer core bead wire

Claims (5)

A carcass composed of a carcass ply extending between a pair of bead portions in a toroidal shape, and a bead core composed of an inner core and an outer core disposed inside and outside in the tire axial direction of the inner end of the carcass ply in the tire radial direction A pneumatic tire including
The inner core and the outer core are each formed by winding one bead wire around the tire rotation axis and spirally in n layers (n is an integer of 3 or more),
In the pneumatic tire, the inner core and the outer core each have a winding start end and a winding end of the bead wire positioned in an outermost layer in the tire radial direction of each core. Each of the inner core and the outer core includes a first portion in which the bead wire is wound in a spiral shape from the winding start end to the innermost layer in a direction of decreasing in diameter toward the inner side in the tire radial direction,
2. The pneumatic tire according to claim 1, wherein the bead wire includes a second portion wound in a spiral shape from the innermost layer to a winding end of the outermost layer in a direction that expands outward in the tire radial direction.   3. The pneumatic tire according to claim 2, wherein each of the inner core and the outer core has a vertically aligned portion in which the bead wire of the first portion and the bead wire of the second portion are vertically aligned in the tire radial direction.   4. The pneumatic tire according to claim 2, wherein each of the inner core and the outer core has a side-by-side portion in which the bead wire of the first portion and the bead wire of the second portion are side-by-side in the tire axial direction.   The pneumatic tire according to claim 4, wherein the side-by-side portions of the inner core and the outer core are formed at equal angles with respect to the tire circumferential direction of the side-by-side portions adjacent to each other in the tire circumferential direction.

Images