JP2008094116A - Pneumatic tire and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance operation stability while ensuring high bead durability. <P>SOLUTION: A bead apex rubber 8 comprises a bottom side 12a, an apex main part 10 and an apex sub-part 11. The apex sub-part 11 is divided to the apex sub-portions 11i, 11o at the inner and outer sides in a tire axial direction by a division line X extending from a first apex P to the outer side in a radial direction. Rubber hardness of the apex main part 10 is 80-95° and complex modulus of elasticity is 15-30 MPa, and rubber hardness of the apex sub-portions 11i, 11o is 50-80° and complex modulus of elasticity is 3-15 MPa. A ratio h1/h2 of heights h1, h2 of the respective apexes P, Q from a bead base line BL is 0.3-0.9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which steering stability is improved while exhibiting excellent bead durability by changing a bead apex rubber, and a manufacturing method capable of manufacturing the pneumatic tire with high production efficiency.

  For example, in a pneumatic tire for a small truck used for a light truck, a van, or the like, since a large load is applied as compared with the tire size, distortion tends to concentrate on the bead portion and tends to be inferior in bead durability.

  Therefore, the present applicant has proposed a bead apex rubber a having a structure as schematically shown in FIG. In this structure, the bead apex rubber a is formed by a base apex portion a1 having a triangular cross section rising from the outer surface in the radial direction of the bead core b, and an upper apex portion a2 that completely covers the base apex portion a1, and the upper apex. The portion a2 is further divided into an upper inner apex portion a2i and an upper outer apex portion a2o in the tire axial direction. The base apex portion a1 is made of hard rubber having a rubber hardness of 85 to 95, the upper inner apex portion a2i is made of a soft rubber with a rubber hardness of 80 to 85, and the upper and outer apex portion a2o is made of a rubber hardness of 75 to 85. In addition, soft rubber is used. Thus, separation between the bead apex rubber a and the carcass ply c is suppressed and bead durability is improved while ensuring bead rigidity.

JP 2003-291613 A

  However, since the bead apex rubber a has a three-layer structure, the structure is complicated and there is a problem in that productivity is reduced. Further, since the base apex portion a1 is completely covered by the upper apex portion a2, the hard base apex portion a1 tends to be excessively miniaturized, and it is disadvantageous in terms of maneuvering stability such as insufficient bead rigidity. It becomes. In order to compensate for this, the upper apex part a2 needs to use a rubber having a rubber hardness of 80 to 85 although it is soft, so that the effect of suppressing the separation is not exhibited so high that the bead durability is improved. Insufficient.

  Accordingly, the present invention provides a pneumatic tire that can suppress a decrease in productivity while having a bead apex rubber having a three-layer structure, and that can improve steering stability while exhibiting excellent bead durability, and its manufacture. It aims to provide a method.

In order to achieve the above-mentioned object, the invention of claim 1 of the present application provides a series of ply turn-up portions that are turned around the bead core in the ply body portion that extends from the tread portion through the sidewall portion to the bead core of the bead portion. A pneumatic tire comprising a carcass made of a carcass ply and a bead apex rubber having a substantially triangular cross section extending radially outward from the bead core,
The bead apex rubber is
A first side intersecting at a first apex radially outwardly extending from a bottom side of the bead core in contact with a radially outer surface, an inner bottom point of an inner end in the tire axial direction of the bottom side, and an outer bottom point of the outer end of the tire axial direction. A hard and highly elastic apex main part having a triangular cross section having an inner hypotenuse and a first outer hypotenuse,
And an inner separation point on the first inner hypotenuse separated radially outward from the inner base point, and an outer separation point on the first outer hypotenuse separated radially outward from the outer base point. And a second inner hypotenuse and a second outer hypotenuse that intersect at a second apex radially outward from the first apex, and at the radially outer sides of the inner and outer separation points A soft and low-elastic apex sub-portion covering the first inner hypotenuse and the first outer hypotenuse,
In addition, the apex sub-portion is divided into an inner apex sub-portion on the inner side in the tire axial direction and an outer apex sub-portion on the outer side in the tire axial direction by a dividing line extending radially outward from the first apex,
The apex main part has a rubber hardness Hs1 of 80 to 95 and a complex elastic modulus E * 1 of 15 to 30 MPa, and the inner apex sub part has a rubber hardness Hs2i of 50 to 80 and a complex elastic modulus E * 2i of 3 to 15 MPa. The outer apex sub-portion has a rubber hardness Hs2o of 50 to 80 and different from the rubber hardness Hs2i, and a complex elastic modulus E * 2o of 3 to 15 MPa and different from the complex elastic modulus E * 2i.
Moreover, the radial height h1 from the bead base line of the first vertex is set to 0.3 to 0.9 times the radial height h2 from the bead base line of the second vertex,
And the thickness ti of the leg portion of the inner apex sub-portion between the first inner hypotenuse and the second inner hypotenuse, and the outer apex sub-portion between the first outer hypotenuse and the second outer hypotenuse. The thickness to of each leg portion is characterized by gradually decreasing from the first apex inward in the radial direction.

  According to a second aspect of the present invention, the apex sub-portion has a radial height h3i from the bead base line at the inner separation point and a radial height h3o from the bead base line at the outer separation point, respectively. It is characterized by being in the range of 0.1 to 0.2 times the cross-sectional height H

  In the invention of claim 3, the radial height h1 of the first vertex from the bead baseline is greater than 0.7 times the radial height h2 of the second vertex from the bead baseline. It is characterized by being 0.9 times or less

  In the invention of claim 4, the dividing line does not pass through the second vertex.

The invention of claim 5 is a pneumatic tire manufacturing method for manufacturing the pneumatic tire according to any one of claims 1 to 4,
A winding step of forming a cylindrical carcass ply wound body by winding the raw carcass ply for forming the carcass ply on the outer peripheral surface of the molding drum,
The apex main portion is formed on the radially outer surface of the bead core and has a triangular cross section at a position where the carcass ply wound body is disposed radially outward and from the edge of the carcass ply wound body to the inner side in the tire axial direction. A core assembly arrangement step of arranging a core assembly provided with apex rubber;
And a ply folding step of folding the carcass ply winding body around the core assembly,
Prior to this ply folding step, an inner rubber sheet for forming the inner apex sub-portion and an outer rubber sheet for forming the outer apex sub-portion are formed on the carcass ply winding body and inside and outside in the tire axial direction of the arrangement position. Are formed in an inner rubber sheet wound body and an outer rubber sheet wound body that are wound in the circumferential direction, and the inner apex rubber is joined to the main apex rubber as the carcass ply wound body is folded in the ply folding process. The sheet winding body and the outer rubber sheet winding body are joined.

  In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified when the bead part is held in accordance with the rim width defined by the tire size in a non-rim assembled state. . The “bead base line” means a tire axial line passing through a bead diameter position defined by a standard based on the tire.

  The “rubber hardness Hs” is a durometer A hardness measured by a durometer type A based on JIS-K6253, and the “complex elastic modulus E *” is measured using a viscoelastic spectrometer at a temperature of 70. It is a value measured under the conditions of ° C., frequency 10 Hz, initial stretch strain 10%, and dynamic strain amplitude ± 2%.

  In the pneumatic tire according to the first aspect of the present invention, only a portion of the hard apex main portion that is radially outward from the inner separation point and the outer separation point is covered with a soft apex sub-portion. Therefore, the apex main part can be enlarged, for example, the ratio of the rubber volume of the apex main part in the bead apex rubber can be increased, and the bead rigidity can be increased and the steering stability can be improved. On the other hand, a softer rubber can be used for the apex sub-part, and the effect of suppressing the separation from the carcass ply can be increased and the bead durability can be improved. In addition, since the apex sub-portion is divided into the inner and outer apex sub-portions, the outer apex sub-portion where separation is more likely to occur can be softened, and steering stability is improved as compared with the case where no division is made. The improvement effect and the improvement effect of bead durability can be further enhanced.

  Further, in the manufacturing method of the second invention, prior to the ply folding step, the wound body of the inner rubber sheet for forming the inner apex sub-portion and the outer rubber sheet for forming the outer apex sub-portion are formed on the carcass ply wound body. And a wound body. Then, by folding the carcass ply roll, the inner rubber sheet roll and the outer rubber sheet roll are joined to the main apex rubber on the bead core side to form a three-layer bead apex rubber. .

  Therefore, it is not necessary to extrude and form the bead apex rubber in a three-layer structure using a rubber extrusion device having a complicated extrusion head, and productivity can be improved. In addition, the shape and size of the apex sub-portion can be freely changed depending on the thickness and width of the inner and outer rubber sheets and the position where the apex is attached to the carcass ply, thus increasing versatility and applying to tires of various sizes. be able to.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a case where the pneumatic tire 1 of the present invention is a light truck tire, and FIG. 2 is an enlarged cross-sectional view showing a bead portion thereof.

  In FIG. 1, a pneumatic tire 1 is disposed on a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, inside the tread portion 2, and radially outside the carcass 6. A belt layer 7;

  The belt layer 7 is formed of two or more belt plies using a belt cord. In this example, the belt layer 7 includes a first belt ply 7A on the innermost side in the radial direction in which steel cords are arranged at an angle of 60 ± 15 ° with respect to the tire circumferential direction, and 10 to 10 with respect to the tire circumferential direction. A case of a three-sheet structure with second and third belt plies 7B and 7C arranged at a small angle of 35 ° is illustrated. The belt plies 7 </ b> A to 7 </ b> C are provided with one or more places where the belt cords intersect between the plies, and are superposed on each other, thereby enhancing the belt rigidity and strongly reinforcing the tread portion 2.

  On the outer side in the radial direction of the belt layer 7, a band layer 9 in which band cords of organic fibers such as nylon are arranged at an angle of, for example, 5 degrees or less with respect to the circumferential direction with the main purpose of improving high-speed durability. Can be provided. As the band layer 9, a pair of left and right edge band plies that covers only the outer end portion in the tire axial direction of the belt layer 7 and a full band ply that covers substantially the entire width of the belt layer 7 can be used as appropriate. An example of one full band ply is shown.

  The carcass 6 is formed of one or more, in this example, two carcass plies 6A and 6B in which carcass cords are arranged at an angle of 75 to 90 ° with respect to the tire circumferential direction. Each of the carcass plies 6A, 6B includes a series of ply folding portions 6b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the ply main body portion 6a straddling the bead cores 5 and 5.

  A bead apex rubber 8 having a triangular cross section extending from the bead core 5 outward in the tire radial direction is provided between the ply main body portion 6a and the ply turn-up portion 6b.

  As shown in an enlarged view in FIG. 2, the bead apex rubber 8 includes a radially inner apex main portion 10 made of hard and highly elastic rubber rising from the radial outer surface 5S of the bead core 5, and the apex main portion 10. It comprises an apex sub-part 11 made of a soft and low-elastic rubber that covers only the radially outer part.

  Specifically, the apex main portion 10 is a bottom 12a that contacts the outer surface 5S of the bead core 5, and an inner bottom point Pi that is the inner end in the tire axial direction of the bottom 12a and extends to a first apex P that is radially outward. 1 has an inner hypotenuse 12i and a first outer hypotenuse 12o extending from the outer base Po which is the outer end in the tire axial direction of the base 12a to the first apex P.

  The outer surface 5S of the bead core 5 means a surface that can be seen when the bead core 5 is viewed from the outside in the radial direction. The bead core 5 has a cross section as shown in FIGS. Various cross-sectional shapes such as a hexagonal shape (including a flat hexagonal shape), a rectangular cross-sectional shape, and a circular cross-sectional shape can be employed.

  Next, the apex sub-part 11 is radially outward from the first vertex P from an inner separation point Qi on the first inner hypotenuse 12i that is spaced radially outward from the inner bottom point Pi. The second apex Q from the second inner hypotenuse 13i extending to the second apex Q and the outer separation point Qo on the first outer hypotenuse 12o spaced radially outward from the outer base Po. A second outer hypotenuse 13o extending to the end. As a result, the apex sub-portion 11 covers the first inner hypotenuse 12i and the first outer hypotenuse 12o on the radially outer side of the inner separation point Qi and the outer separation point Qo.

  Further, the apex sub-part 11 is divided into an inner apex sub-part 11i on the inner side in the tire axial direction and an outer apex sub-part 11o on the outer side in the tire axial direction by a dividing line X extending radially outward from the first apex P. It is divided. The dividing line X preferably crosses the second inner hypotenuse 13i or the second outer hypotenuse 13o at an intersection J without passing through the second vertex Q, and particularly as in this example, the second inner hypotenuse 13i or the second outer hypotenuse 13o intersects. It is preferable to intersect with the hypotenuse 13i. That is, the dividing line X intersects with the second inner hypotenuse 13i at the intersection J, and the radial height h4 from the bead base line BL of the intersection J is larger than the height h1 and smaller than the height h2.

  Here, the apex main part 10 has a rubber hardness Hs1 in the range of 80 to 95 ° and a complex elastic modulus E * 1 in the range of 15 to 30 MPa in order to sufficiently secure the bead rigidity and enhance the steering stability. The bead base of the second apex Q is made of hard and highly elastic rubber, and the height h1 in the radial direction from the bead base line BL of the first apex P, that is, the height h1 of the apex main portion 10 is set. The height h2 in the radial direction from the line BL, that is, the range of 0.3 to 0.9 times the total height h2 of the bead apex rubber 8, preferably 0.5 times or more. At this time, in this example, the total height h2 of the bead apex rubber 8 is set in a range of 0.3 to 0.5 times the tire cross-section height H (shown in FIG. 1).

  In the apex main part 10, when the rubber hardness Hs1 is less than 80 °, the complex elastic modulus E * 1 is less than 15 MPa, and the height h1 is less than 0.3 times the height h2, the bead rigidity As a result, the steering stability tends to decrease. Conversely, when the rubber hardness Hs1 is greater than 95 °, the complex elastic modulus E * 1 is greater than 30 MPa, and the height h1 is greater than 0.9 times the height h2, the bead apex rubber 8 is hardened. As a result, the heat generation at the bead part 4 becomes large, the difference in rigidity with the apex sub part 11 becomes excessive and stress is concentrated, and the shear strain relaxation effect by the apex sub part 11 is reduced. Therefore, the effect of improving the bead durability, which is the object of the present invention, cannot be effectively exhibited. In addition, the ride comfort is also disadvantageous.

  Next, the inner apex sub-portion 11i and the outer apex sub-portion 11o have rubber hardness Hs2i and Hs2o in the range of 50 to 80 °, and complex elastic modulus E * 2i and E * 2o of 3 to 15 MPa. The rubber is softer and less elastic than the apex main part 10. The rubber hardness Hs2i and the complex elastic modulus E * 2i of the inner apex sub-portion 11i are different from the rubber hardness Hs2o and the complex elastic modulus E * 2o of the outer apex sub-portion 11o. In this example, Hs2i> Hs2o, E * A preferable case of 2i> E * 2o is illustrated.

  As described above, in the bead apex rubber 8 according to the present invention, only the portion of the apex main portion 10 that is radially outward from the inner separation point Qi and the outer separation point Qo is covered with the apex sub-portion 11. Yes. Accordingly, the apex main portion 10 can be relatively enlarged, for example, the ratio of the rubber volume of the apex main portion 10 to the bead apex rubber 8 can be increased. As a result, even when softer and less elastic rubber is used for the apex sub-part 11, the bead rigidity can be sufficiently secured and the steering stability can be improved.

  On the other hand, the apex sub-portion 11 covers a radially outward portion of the apex main portion 10 which is a portion where separation is likely to occur. In addition, as described above, a softer and less elastic rubber is used for the apex sub-part 11. Therefore, the effect of reducing the shear strain between the bead apex rubber 8 and the carcass ply can be greatly increased, and the effect of improving the bead durability can be further enhanced while increasing the bead rigidity.

  Moreover, the apex sub-part 11 is divided into apex sub-parts 11i and 11o. Accordingly, the rubber hardness Hs2o and the complex elastic modulus E * 2o of the outer apex sub-part 11o that are relatively unlikely to separate from the carcass ply 6A are reduced. It can be set smaller than the elastic modulus E * 2i. As a result, the steering stability improvement effect and the bead durability improvement effect can be further enhanced.

  In the apex sub-parts 11i and 11o, when the rubber hardness Hs2i and Hs2o is greater than 80 ° and the complex elastic moduli E * 2i and E * 2o are greater than 15 MPa, the bead durability is improved as described above. Cannot be increased sufficiently. On the contrary, when the rubber hardness Hs2i, Hs2o is less than 50 ° and the complex elastic modulus E * 2i, E * 2o is less than 3 MPa, the bead rigidity is insufficient and the effect of improving the steering stability is sufficiently enhanced. Can not be. From such a viewpoint, the lower limit values of the rubber hardness Hs2i and Hs2o are 55 or more and the upper limit values are preferably 75 or less, and the lower limits of the complex elastic modulus E * 2i and E * 2o are 5 MPa or more and the upper limits. The value is preferably 13 MPa or less. The rubber hardness difference | Hs2i-Hs2o | is preferably 5 or more, and the complex elastic modulus difference | E * 2i-E * 2o | is preferably 1 MPa or more.

  Of the rubber hardness Hs2i and Hs2o, the larger rubber hardness is Hs2, and the larger one of the complex elastic moduli E * 2i and E * 2o is E * 2. (Hs1-Hs2) is preferably in the range of 5 to 15, and (difference E * 1-E * 2) of the complex elastic modulus is preferably in the range of 1 to 3 MPa.

  In particular, it is possible to set the height h1 of the apex main portion 10 to be higher than 0.7 and not more than 0.9 times the total height h2 of the bead apex rubber 8, so that the steering stability and the bead durability are set. It is more preferable from the viewpoint of balance with sex. For the same reason, it is preferable that the height h1 is set to be higher than 0.20 times, more preferably 0.25 times higher than the tire cross-section height H within the above range. The height h4 of the intersection point J is preferably smaller than (h1 + h2) / 2.

  In the bead apex rubber 8, the radial height h3i from the bead base line BL of the inner separation point Qi and the radial height h3o from the bead base line BL of the outer separation point Qo are respectively defined as the tire cross-sectional height. It is also important to regulate to a range of 0.1 to 0.2 times the height H. This is because the effect of improving the bead durability tends to be reduced if the upper limit side and the lower limit side are deviated from the range of 0.1 to 0.2 times, respectively. The reason is that the apex strength is insufficient. Is presumed to be the cause.

  At this time, it is also preferable that the radial distances hqi and hqo from the radially outer edge of the bead core 5 of the inner separation point Qi and the outer separation point Qo are each 10 mm or more.

  In the apex sub-part 11, the thickness ti of the leg part 11iA (referred to as the inner leg part 11iA for convenience) of the inner apex sub-part 11i between the first inner hypotenuse 12i and the second inner hypotenuse 13i, The thickness to of the leg portion 11oA (referred to as the outer leg portion 11oA for convenience) of the outer apex sub-portion 11o between the first outer hypotenuse 12o and the second outer hypotenuse 13o is the first apex, respectively. It gradually decreases from P inward in the radial direction. Thereby, the balance of bead rigidity and bead durability is kept higher. At each height position in the radial direction, the ratio ti / to between the thickness ti of the inner leg 11iA and the thickness to of the outer leg 11oA is in the range of 0.7 to 1.4. Is preferred. The thicknesses ti and to are measured at respective height positions on the first inner hypotenuse 12i and the first outer hypotenuse 12o.

Next, a method for manufacturing such a pneumatic tire 1 will be described.
In this manufacturing method,
(1) A winding step S1 (FIG. 5A) for winding the green carcass ply 6N for forming the carcass ply around the outer peripheral surface of the forming drum 30 to form a cylindrical carcass ply wound body 6NR;
(2) The apex main part is formed on the radially outer surface of the bead core 5 at a position K that is located radially outward of the carcass ply wound body 6NR and at the inner side in the tire axial direction from the edge of the carcass ply wound body 6NR. A core assembly placement step S2 (FIG. 5B) for placing a core assembly 31 provided with a triangular main apex rubber 10N.
(3) including a ply folding step S3 (FIG. 5C) for folding the carcass ply wound body 6NR around the core assembly 31;
(4) Prior to the ply folding step S3, the inner rubber sheet 11Ni for forming the inner apex sub-portion and the outer apex sub-portion are formed on the carcass ply wound body 6NR and inside and outside the arrangement position K in the tire axial direction. An inner rubber sheet winding body 11NRi and an outer rubber sheet winding body 11NRo, in which the outer rubber sheet 11No for partial formation is wound in the circumferential direction, are formed.
In FIG. 5, reference numeral 33 denotes a ply folding bladder, and reference numeral 34 denotes a holding ring that holds the core assembly 31.

  Accordingly, as shown in FIG. 5C, the inner rubber sheet wound body 11NRi and the outer rubber sheet wound body 11NRo are attached to the main apex rubber 10N of the core assembly 31 by turning the carcass ply wound body 6NR. The bead apex rubber 8 having a three-layer structure that is integrally joined to each other can be formed.

  Thus, in the manufacturing method, it is not necessary to extrude and form the bead apex rubber 8 in a three-layer structure using a rubber extrusion device having a complicated extrusion head, and productivity can be improved. Also, the shape and size of the apex sub-part 11 can be freely changed according to the thickness and width of the inner and outer rubber sheets 11Ni and 11No and the position where the apex is attached to the carcass ply 6N. It can be easily applied to tires.

  In this example, as the raw carcass ply 6N, a composite raw carcass ply 6NA in which an inner rubber sheet 11Ni and an outer rubber sheet 11No are bonded in advance to the outer surface of the raw carcass ply 6N is used. In the winding step S1, the carcass ply wound body 6NR and the inner and outer rubber sheet wound bodies 11NRi and 11NRo are simultaneously formed by winding the composite raw carcass ply 6NA. In this case, productivity can be further increased.

  The carcass ply wound body 6NR is once formed by the winding step S1, and then the rubber sheets 11Ni and 11No are wound on the outer surface to form the rubber sheet wound bodies 11NRi and 11NRo.

  As mentioned above, although 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 small truck tire having the basic configuration shown in FIG. 1 and having a tire size of 195 / 85R16 was made on the basis of the specifications in Table 1, and the bead durability and the handling stability of each sample tire were tested and compared. . Each tire has the same specifications except that the bead apex rubber is different, and the total height h2 of the bead apex rubber is the same as 0.4 times the tire cross-sectional height H. FIG. 6 shows the structure of the bead apex rubber of Comparative Example 1 in Table 1. Further, as shown in FIG. 3, the thicknesses ti1 and to1 in the table are the thicknesses ti and to of the inner leg 11iA and the outer leg 11oA at the first vertex P, and the thicknesses ti2 and to2 are Means the thicknesses ti and to of the leg portions 11iA and 11oA at the height of 3/4 · h1 separating the height 3/4 of the height h1 from the bead base line BL.

(1) Bead durability;
A sample tire is run on a drum at a speed of 20 km / H with a rim (16 × 5.5K), internal pressure (600 kPa), and a longitudinal load that is 2.0 times (23.2 KN) the maximum load of JATMA standard. At the same time, the running time until the tire breaks is measured and displayed as an index with Comparative Example 1 as 100. A larger index is better.

(2) Steering stability;
A sample tire is mounted on all the wheels of a two-story domestic light truck under the conditions of a rim (16 x 5.5K) and internal pressure (600 kPa), and runs on a dry asphalt road tire test course with one driver In addition, the steering stability (steering response, rigidity, grip, etc.), ride comfort, etc. are comprehensively evaluated based on the driver's sensation, and the comparative example 1 is displayed as an index of 100. A larger index is better.

  As shown in Table 1, it can be confirmed that the tires of the examples can improve steering stability while ensuring high bead durability.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which expands and shows the bead part. It is sectional drawing which expands a bead apex rubber further. (A)-(C) are sectional drawings explaining the outer surface of a bead core. (A)-(C) are drawings explaining the manufacturing method of a tire. It is sectional drawing which shows the structure of the bead apex rubber | gum in the comparative example 1 in a table | surface. It is sectional drawing of the bead part explaining background art.

Explanation of symbols

2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A, 6B Carcass ply 6a Ply body part 6b Ply turn part 6N Raw carcass ply 6NR Carcass ply roll 8 Bead apex rubber 10 Apex main part 10N Main apex rubber 11 Apex Sub part 11i Inner apex sub part 11o Outer apex sub part 11iA, 11oA Leg part 11Ni Inner rubber sheet 11No Outer rubber sheet 11NRi Inner rubber sheet roll 11NRo Outer rubber sheet roll 12a Bottom 12i First inner hypotenuse 12o First Outer hypotenuse 13i Second inner hypotenuse 13o Second outer hypotenuse 30 Molding drum 31 Core assembly BL Bead base line K Arrangement position S1 Winding step S2 Core assembly arrangement step S3 Ply folding step P First vertex Pi Bottom point Po outsole point Q second vertex Qi inner spaced points Qo outer spaced points X dividing line

Claims (5)

A carcass made of a carcass ply provided with a series of ply turn-up portions that are folded around the bead core in a ply main body portion that extends from the tread portion to the bead core through the sidewall portion, and radially outward from the bead core. A pneumatic tire comprising a bead apex rubber with a triangular cross-section extending,
The bead apex rubber is
A first side intersecting at a first apex radially outwardly extending from a bottom side of the bead core in contact with a radially outer surface, an inner bottom point of an inner end in the tire axial direction of the bottom side, and an outer bottom point of the outer end of the tire axial direction. A hard and highly elastic apex main part having a triangular cross section having an inner hypotenuse and a first outer hypotenuse,
And an inner separation point on the first inner hypotenuse separated radially outward from the inner base point, and an outer separation point on the first outer hypotenuse separated radially outward from the outer base point. And a second inner hypotenuse and a second outer hypotenuse that intersect at a second apex radially outward from the first apex, and at the radially outer sides of the inner and outer separation points A soft and low-elastic apex sub-portion covering the first inner hypotenuse and the first outer hypotenuse,
In addition, the apex sub-portion is divided into an inner apex sub-portion on the inner side in the tire axial direction and an outer apex sub-portion on the outer side in the tire axial direction by a dividing line extending radially outward from the first apex,
The apex main part has a rubber hardness Hs1 of 80 to 95 and a complex elastic modulus E * 1 of 15 to 30 MPa, and the inner apex sub part has a rubber hardness Hs2i of 50 to 80 and a complex elastic modulus E * 2i of 3 to 15 MPa. The outer apex sub-portion has a rubber hardness Hs2o of 50 to 80 and different from the rubber hardness Hs2i, and a complex elastic modulus E * 2o of 3 to 15 MPa and different from the complex elastic modulus E * 2i.
Moreover, the radial height h1 from the bead base line of the first vertex is set to 0.3 to 0.9 times the radial height h2 from the bead base line of the second vertex,
And the thickness ti of the leg portion of the inner apex sub-portion between the first inner hypotenuse and the second inner hypotenuse, and the outer apex sub-portion between the first outer hypotenuse and the second outer hypotenuse. The pneumatic tire is characterized in that the leg thickness to decreases gradually from the first apex inward in the radial direction.   The apex sub-portion has a radial height h3i from the bead base line of the inner separation point and a radial height h3o from the bead base line of the outer separation point to a tire cross-sectional height H of 0.1. The pneumatic tire according to claim 1, which is in a range of about 0.2 times.   The radial height h1 from the bead baseline of the first vertex is greater than 0.7 times and less than 0.9 times the radial height h2 from the bead baseline of the second vertex. The pneumatic tire according to claim 1 or 2.   The pneumatic tire according to claim 1, wherein the dividing line does not pass through the second vertex. A pneumatic tire manufacturing method for manufacturing the pneumatic tire according to claim 1,
A winding step of forming a cylindrical carcass ply wound body by winding the raw carcass ply for forming the carcass ply on the outer peripheral surface of the molding drum,
The apex main part is formed on the radially outer surface of the bead core at a position arranged in the radial direction outer side of the carcass ply wound body and on the inner side in the tire axial direction from the end edge of the carcass ply wound body. A core assembly placement step for placing a core assembly provided with a main apex rubber;
And a ply folding step of folding the carcass ply winding body around the core assembly,
Prior to this ply folding step, an inner rubber sheet for forming the inner apex sub-portion and an outer rubber sheet for forming the outer apex sub-portion are formed on the carcass ply winding body and inside and outside in the tire axial direction of the arrangement position. Are formed in an inner rubber sheet wound body and an outer rubber sheet wound body that are wound in the circumferential direction, and the inner apex rubber is joined to the main apex rubber as the carcass ply wound body is folded in the ply folding process. A method for manufacturing a pneumatic tire, characterized in that a sheet winding body and an outer rubber sheet winding body are joined.

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