JP2008062759A - Heavy load tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit poor inflation of a tire and improving uniformity of PRO or the like. <P>SOLUTION: This tire is provided with a carcass 6 including a carcass turnaround part 6b turned around a bead core 5. The bead core 5 includes a core body 10 repeatedly winding bead wire 5w, and a lapping layer 11 covering a perimeter thereof. The core body 10 has polygon shape section having a surface facing a rim seat Rs formed in a flat core bottom surface SL. A projection part 13 of a crescent shape section projecting in a convex arc shape toward the rim seat Rs from the core bottom surface SL and making the carcass turnaround part 6b touch the lapping layer 11 between the core bottom surface SL and the lapping layer 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heavy duty tire in which a rubber gauge on a radially inner side of a core body of a bead core is stabilized.

  As shown in FIG. 8, a high-rigidity bead core b is disposed on the bead portion a of the pneumatic tire in order to reinforce the bead portion a and sufficiently ensure the fitting force with the rim. The bead core b includes a ring-shaped core body b1 around which bead wires such as hard steel wires are wound, and a wrapping layer b2 covering the periphery thereof. Usually, the bead core b is attached to the rim sheet so as to be stably seated on the rim sheet. It is formed in a polygonal cross section with the facing surface being a flat core bottom surface bs (see, for example, Patent Document 1).

JP 2005-8071 A

  Around the bead core b, both end portions of the carcass c forming the tire skeleton are folded back, whereby both end portions of the carcass c are fixed. Reference numeral d denotes a bead reinforcement layer that covers the carcass c in a U shape.

  Here, in a tire in which a carcass cord is formed of a steel cord, such as a heavy load tire, since the bending rigidity of the carcass c is high, the core bottom surface bs of the bead core b and the carcass c are not in close contact with each other, and the gap portion having a crescent cross section is used. e is formed. This gap e exists as an air pocket at the stage of the raw tire before vulcanization. At the time of vulcanization molding, the air in the gap e flows through the carcass cord by pressure contact with the beet ring forming the vulcanization mold, while a part of the topping rubber of the carcass c passes through the front gap e. It flows into and forms a rubber reservoir.

  However, at this time, the rubber volume in the gap portion e depends on the amount of the topping rubber flowing in, and thus has a large variation and is unstable. Therefore, under the bead core, the rubber gauge g1 between the bead core b and the carcass c, and between the carcass c and the bead base surface (if there is a bead reinforcement layer d, between the bead reinforcement layer d and the bead base surface). There is a problem in that the bead core lower gauge which is the rubber gauge g2 of the rubber gauge is unevenly distributed in the tire circumferential direction, and uniformity such as RRO (radial run out) is lowered. In addition, during vulcanization molding, the air flowing out from the gap e causes a tire air deficiency such as forming a new air pocket in the sidewall portion where the action of pressure is relatively low.

  Therefore, the present invention is based on the provision of a bulged portion having a crescent cross section that protrudes in a convex arc shape toward the rim sheet between the core body and the wrapping layer, and generates a gap between the carcass and the bead core. An object of the present invention is to provide a heavy-duty tire that can be suppressed, can improve the uniformity of the RRO and the like by making the gauge below the bead core uniform, and can suppress poor air entry of the tire.

In order to achieve the above object, the invention of claim 1 of the present application includes a carcass main body extending from a tread portion to a bead core of a bead portion through a side wall portion, and a carcass folded around the bead core connected to the carcass main body portion. A heavy duty tire comprising a carcass having a folded portion and the bead portion is seated and attached to a rim seat of a rim,
The bead core includes a ring-shaped core body formed by winding bead wires, and a wrapping layer that covers the periphery of the core body and prevents the bead wires from being loosened.
In the cross section including the tire shaft, the core body has a polygonal shape having a flat core bottom surface facing the rim seat,
Further, a bulging portion having a crescent-shaped cross section is formed between the core bottom surface and the wrapping layer so as to protrude in a convex arc shape from the core bottom surface toward the rim sheet, and the carcass folded portion is in contact with the wrapping layer. It is characterized by.

According to a second aspect of the present invention, the bulging portion is formed of a hard rubber layer having a rubber hardness Hs of 80 to 93.
According to a third aspect of the present invention, the bulging portion includes an auxiliary cord layer in which a plurality of cord arrays in which auxiliary cords extending in the tire circumferential direction are arranged in the tire axial direction are overlapped in the radial direction. It is a feature.
According to a fourth aspect of the present invention, the bulging portion includes a cord array in which auxiliary cords arranged in the tire circumferential direction are arranged in the tire axial direction and a hard rubber layer having a rubber hardness of 80 to 93 inward and outward in the radial direction. It is characterized by comprising composite layers that are stacked.
In the invention of claim 5, the core body has a core upper surface parallel to the core bottom surface on the radially outer side, and a protruding height t of the bulging portion from the core bottom surface is determined by the core of the core body. It is characterized by being 0.2 to 0.4 times the core thickness T, which is the distance between the bottom surface and the core top surface.

  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 rubber hardness Hs is a durometer A hardness measured with a durometer type A based on JIS-K6253.

  As described above, the present invention provides a bead core having a core body having a flat core bottom surface facing the rim sheet and a wrapping layer covering the periphery of the core body, and the core bottom surface between the core body and the wrapping layer. A bulging portion having a crescent-shaped cross section that protrudes in a convex arc shape toward the rim sheet and contacts the carcass folded portion with the wrapping layer is formed.

  Therefore, even in the case of a heavy duty tire having a large bending rigidity of the carcass, it is possible to prevent a gap from being formed between the bead core and the carcass folded portion under the bead core. As a result, variations in the tire circumferential direction of the bead core lower gauge due to the formation of the gap can be suppressed, and uniformity such as RRO (radial runout) can be improved. Further, since the gap portion is not formed, there is no occurrence of air accumulation, and it is possible to suppress the poor air entry of the tire caused by it.

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

  As shown in FIGS. 1 and 2, the heavy load tire 1 of the present embodiment 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 the carcass 6 radially outward. A belt layer 7 disposed inside the tread portion 2. The heavy load tire 1 is attached with the bead portion 4 seated on the rim seat Rs of the rim R.

  The belt layer 7 is composed of at least three steel belt plies using steel cords as belt cords. In this example, the first belt ply 7A on the innermost side in the radial direction in which the belt cord is arranged at an angle of, for example, 60 ± 15 ° with respect to the tire circumferential direction, and a small size of, for example, 10 to 35 ° with respect to the tire circumferential direction. The thing of the 4 sheet structure which consists of the 2nd-4th belt plies 7B-7D arranged at an angle is illustrated. The belt layer 7 has one or more locations where the belt cords cross each other between the plies, thereby increasing the belt rigidity and reinforcing the tread portion 2 with a tagging effect.

  The carcass 6 includes a carcass body portion 6a straddling the bead cores 5 and 5, and a carcass folding portion that is connected to the carcass body portion 6a and is folded around the bead core 5 from the inner side to the outer side in the tire axial direction. 6b. In this example, the case where the carcass folding portion 6b is folded around the bead core 5 and then rolled up radially outward (for convenience, referred to as a winding structure) is illustrated, but as illustrated in FIG. The carcass folded portion 6b may be wound around the bead core 5 almost once and cut off (referred to as a winding structure for convenience). In the case of a roll-up structure, a bead reinforcement bead apex rubber 8 is provided between the carcass main body portion 6a and the carcass folding portion 6b so as to taper outward from the bead core 5 in the radial direction. In the case of the structure, the bead apex rubber 8 extends in a tapered shape from the bead core 5 toward the outside in the radial direction via the carcass folded portion 6b.

  The bead apex rubber 8 includes a radially inward lower pex portion 8a made of a hard rubber layer having a rubber hardness Hs1 of, for example, 80 to 95, and a radially outward upper apex portion 8b made of a softer rubber. Formed from. In this example, the rubber hardness Hs2 of the upper apex portion 8b is, for example, in the range of 50 to 65. This reduces the shear stress that acts on the carcass folded portion 6b during bead deformation, thereby separating the carcass folded portion 6b. To prevent.

  The bead portion 4 is provided with a bead reinforcing layer 9 for the purpose of further reinforcing the bead portion 4. This bead reinforcing layer 9 is made of a cord ply in which steel cords are arranged at an angle of, for example, 10 to 60 ° with respect to the tire circumferential direction line, and as shown in FIG. 2, on both sides of the bottom piece 9a passing under the bead core, The inner piece 9i extending along the tire axial direction inner side surface of the carcass main body 6a and the outer piece 9o extending along the tire axial direction outer side surface of the carcass folded portion 6b are formed in a U-shaped cross section. The inner piece 9i and the outer piece 9o have a radial height hi, ho from the bead base line BL to prevent damage from the radially outer end, and the bead at the outer end of the carcass folded portion 6b. It is set to be smaller than the radial height h1 from the base line BL.

  Reference numeral 20 in the drawing denotes a clinching rubber for preventing rim misalignment. In this example, a base portion 20a that forms a bead base surface 4s, which is a radially inner surface of the bead portion 4, and a radial direction from the outer end in the tire axial direction. A rising portion 20b that forms a bead outer surface is provided in a region that rises outward and contacts at least the rim flange. The rubber hardness Hs3 of the clinch rubber 20 is larger than the rubber hardness Hs2 and smaller than the rubber hardness Hs1, and in this example, the radial height h2 from the bead base line BL at the outer end of the rising portion 20b. Is larger than the radial height h3 from the bead base line BL at the outer end of the hard lower apex portion 8a and larger than the radial height h4 from the bead base line BL at the outer end of the soft upper apex portion 8b. As a small, the rigidity balance of the bead part 4 is optimized.

  Next, the bead core 5 covers a ring-shaped core body 10 formed by winding a steel bead wire 5w such as a hard steel wire and the periphery of the core body 10 to prevent the bead wire 5w from being scattered. And the wrapping layer 11 to be configured.

  In the meridional section including the tire axis, the core body 10 has a polygonal shape such as a quadrangular shape, a pentagonal shape, a hexagonal shape, or the like, in which the surface facing the rim sheet Rs is a flat core bottom surface SL. When the core bottom surface SL is a flat surface, the fitting force to the rim sheet Rs can be increased over a wide range. Further, the seating of the bead core 5 with respect to the rim seat Rs is stabilized, and the bead deformation in the rotational direction around the center of the cross section of the bead core 5 can be effectively suppressed. Further, in the core body 10 of this example, as shown in an enlarged view in FIG. 3, in order to obtain a higher fitting force with a small amount of steel, a core upper surface SU parallel to the core bottom surface SL is provided on the outer side in the radial direction. Even-angled shapes such as a quadrangular shape and a hexagonal shape, in particular, the length L1 of the core bottom surface SL is greater than 1.0 times the core thickness T which is the distance between the core bottom surface SL and the core top surface SU, preferably Adopts a horizontally long flat cross section of 1.4 times or more. The core bottom surface SL is preferably inclined substantially in parallel with the rim sheet Rs. In this example, the case where the rim R is a tubeless 15 ° taper rim is illustrated, and therefore the core bottom surface SL is approximately 15 ° with respect to the tire axial line, specifically 15 ° ± 2 °. It is inclined at an angle θ.

  The wrapping layer 11 covers the periphery of the core body 10 to prevent the bead wire 5w from being scattered. As the wrapping layer 11, a wrapping sheet having a structure in which a wrapping cord is spirally wound around the core body 10, or a wrapping sheet such as a rubber sheet and a rubberized cloth having a canvas cloth in the rubber sheet is used. The thing of the structure wound around the core main body 10 etc. can be employ | adopted suitably. ,

  In the present invention, between the core bottom surface SL and the wrapping layer 11, as shown in an enlarged manner in FIGS. 3 to 6, the core bottom surface SL protrudes in a convex arc shape toward the rim sheet Rs, and the carcass folded back A bulging portion 13 having a crescent-shaped cross section for contacting the portion 6b with the wrapping layer 11 is formed.

  In this way, the bulging portion 13 protrudes in a convex arc shape from the core bottom surface SL, thereby eliminating the conventional formation of a gap portion formed between the carcass folded portion 6b and the wrapping layer 11 under the bead core. it can. As a result, the rubber gauge g2 between the carcass 6 and the bead base surface 4s (between the bead reinforcement layer 9 and the bead base surface when there is a bead reinforcement layer 9) is stabilized, and the rubber gauge g2 is in the tire circumferential direction. It is possible to prevent a decrease in uniformity such as RRO (radial run-out) due to unevenness. In addition, since air can be prevented from accumulating in the gap portion when forming a raw tire, it is possible to suppress tires from entering the air.

  For this purpose, the protruding height t of the bulging portion 13 from the core bottom surface SL is preferably in the range of 0.2 to 0.4 times the core thickness T, and less than 0.2 times The bulging portion 13 is too small, air can easily enter, and uniformity cannot be exhibited. On the other hand, even if it exceeds 0.4 times, the bulging portion 13 is too large to sufficiently exhibit the above effect.

Further, when the bulging portion 13 is soft, the bulging portion 13 is deformed due to rubber flow or the like during vulcanization molding, and there is a tendency that the fitting force with the rim is insufficient and steering stability is reduced. . Therefore,
(1) The bulging portion 13 is formed of a hard rubber layer 14 (shown in FIG. 3) having a rubber hardness Hs4 of 80 to 93:
(2) Auxiliary cord layer 15 (shown in FIG. 4) in which a plurality of cord arrays 15A, in which the bulging portion 13 is arranged in the tire axial direction and auxiliary cords 15a extending in the tire circumferential direction, are placed inside and outside in the radial direction. (3) The bulging portion 13 includes a cord array 15A in which auxiliary cords 15a extending in the tire circumferential direction are arranged in the tire axial direction, and a hard rubber layer 14 having a rubber hardness Hs4 of 80 to 93. Formed with a composite layer 16 (shown in FIGS. 5 and 6) overlaid radially in and out:
It is preferable.

  In the case of the first embodiment in which the bulging portion 13 is composed of a hard rubber layer 14 (shown in FIG. 3), the rubber hardness Hs4 is 80 to 93, which is harder than the clinch rubber 20 and in the unvulcanized state, the rubber flow Therefore, the shape of the bulging portion 13 can be maintained with high accuracy and stability.

  In the case of the second embodiment in which the bulging portion 13 includes the auxiliary cord layer 15 (shown in FIG. 4), an organic fiber cord such as nylon or polyester can be suitably used as the auxiliary cord 15a. If necessary, a steel cord and a wrapping cord can be used as the auxiliary cord 15a. Then, it is preferable to form the cord array 15A by winding a rubberized cord in which the periphery of the auxiliary cord 15a is covered with a topping rubber in a spiral manner in the tire circumferential direction. The number of code arrays in the upper code array 15A1 in the radial direction is smaller than the number of code arrays in the lower code array 15A2. In the case of the second embodiment, a soft rubber smaller than the rubber hardness Hs4 can be adopted as the topping rubber of the cord array 15A.

  In the case of the third embodiment in which the bulging portion 13 is composed of the composite layer 16 (shown in FIGS. 5 and 6), the cord array 15A may be superposed inside the rubber layer 14 in the radial direction, or conversely in the radial direction. It may be placed outside.

  In addition, in order to further press the deformation of the bulging portion 13 due to the rubber flow during vulcanization molding, it is also preferable that the bulging portion 13 is semi-vulcanized or vulcanized prior to vulcanization molding. .

  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 heavy-duty tire having a tire size of 11R22.5 and having the structure shown in FIG. And while comparing the uniformity of each sample tire, it compared the incidence of defective air entry when manufacturing each sample tire.

  In the case of the first embodiment where the bulging portion is made of a rubber layer and the case of the third embodiment where the bulging portion is made of a composite layer, the composition of the rubber used for the rubber layer is as shown in Table 2. The complex elastic modulus in Table 2 is a value measured using a viscoelastic spectrometer under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial tensile strain of 10%, and a dynamic strain amplitude of ± 2%. In the case of the second embodiment in which the bulging portion is composed of an auxiliary cord layer and in the case of the third embodiment comprising a composite layer, the cord array uses nylon cord (940 dtex / 2) as an auxiliary cord. It is wound spirally in the tire circumferential direction. A rubber sheet (thickness 0.9 mm) is used as the wrapping layer.

<Air-filled defects>
The incidence (%) of defective air entry when 500 sample tires were formed was compared.

<Uniformity>

  The RRO (radial runout) of each sample tire was measured with a rim (22.5 × 8.25) and an internal pressure (725 kPa), and the average value was displayed as an index with Comparative Example 1 being 100. A smaller index is better.

  As shown in Table 1, it can be confirmed that in the tires of the examples, the occurrence of poor air entry is suppressed and the uniformity of RRO and the like is improved.

It is sectional drawing which shows one Example of the tire for heavy loads 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 sectional drawing which shows the other Example of a bulging part. It is sectional drawing which shows the further another Example of a bulging part. It is sectional drawing which shows the further another Example of a bulging part. It is sectional drawing which shows the other Example of the folding structure of a carcass. It is sectional drawing explaining the problem of a prior art.

Explanation of symbols

2 tread portion 3 side wall portion 4 bead portion 5 bead core 5w bead wire 6 carcass 6a carcass main body portion 6b carcass folded portion 10 core main body 11 wrapping layer 13 bulging portion 14 rubber layer 15 auxiliary cord layer 15a auxiliary cord 15A code array 16 composite Layer R Rim Rs Rim sheet SL Core bottom SU Core top

Claims (5)

A carcass body having a carcass body portion extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a carcass fold portion connected to the carcass body portion and folded around the bead core; and the bead portion of the rim A heavy-duty tire that is seated and attached to a rim seat,
The bead core includes a ring-shaped core body formed by winding bead wires, and a wrapping layer that covers the periphery of the core body and prevents the bead wires from being loosened.
The core body has a polygonal shape in which a surface facing the rim seat is a flat core bottom surface in a cross section including a tire shaft,
Further, a bulging portion having a crescent-shaped cross section is formed between the core bottom surface and the wrapping layer so as to protrude in a convex arc shape from the core bottom surface toward the rim sheet, and the carcass folded portion is in contact with the wrapping layer. Heavy duty tire characterized by   The heavy-duty tire according to claim 1, wherein the bulging portion is formed of a hard rubber layer having a rubber hardness Hs of 80 to 93.   The said bulging part consists of an auxiliary | assistant cord layer which piled up the several code | cord | chord arrangement body in which the auxiliary | assistant code | cord | chord extended in a tire circumferential direction was arranged in the tire axial direction on both sides in the radial direction. Heavy duty tire.   The bulging portion includes a cord array in which auxiliary cords extending in the tire circumferential direction are arranged in the tire axial direction and a composite layer in which a hard rubber layer having a rubber hardness Hs of 80 to 93 is placed inside and outside in the radial direction. The heavy duty tire according to claim 1, wherein:   The core body has a core top surface parallel to the core bottom surface on the radially outer side, and a protruding height t of the bulging portion from the core bottom surface is a distance between the core bottom surface and the core top surface of the core body. The heavy duty tire according to any one of claims 1 to 4, wherein the tire thickness is 0.2 to 0.4 times the core thickness T.

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