JP2018070064A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire capable of reducing the weight of a tire and suppressing the air entering around a folded portion of a carcass ply. A pneumatic tire according to the present invention includes a pair of bead cores, a main body portion continuously extending in a toroidal shape between the pair of bead cores, a continuous extension from the main body portion, and a periphery of the bead core. A carcass made of only one carcass ply, and a carcass ply turn-up portion, the carcass ply turn-up portion being wound around the tire width direction inside from the tire width direction outside. The tire radial direction length L1 from the tire radial direction inner side end of the carcass ply to the tire radial direction inner side end of the carcass ply is 4 to 45 mm. The carcass ply cord constituting the carcass ply has a fineness of 5000 to 9100 dtex and a bending resistance of 30 to 1 Is 0mN. [Selection] Figure 1

Description

  The present invention relates to a pneumatic tire.

  Conventionally, there is a pneumatic tire provided with a carcass formed by stacking two to three carcass plies (for example, Patent Document 1).

JP 2011-207319 A

In recent years, tires with low fuel consumption have been demanded, and one countermeasure is to reduce the weight of the tires in order to reduce rolling resistance. One way to reduce the weight of a tire is to reduce the number of carcass plies to one while increasing the cord diameter of the carcass ply, so that the carcass consists of a plurality of carcass plies. It is conceivable to reduce the total amount of rubber.
However, when a carcass with a thick carcass ply cord diameter is used, an unvulcanized carcass ply (also referred to as a “treat”) is folded around the bead core on the green tire molding drum when the green tire is manufactured. When forming the folded portion of the uncured carcass ply, for example, even if it is bent with a small bending radius and along the main body of the uncured carcass ply, there is a possibility that it cannot be bent as expected. It was. Therefore, in the finally completed tire, the remaining air (hereinafter referred to as “the remaining portion of the air between the folded portion of the carcass ply and the tire constituent portion (such as the bead filler, bead core, or carcass ply main body)) disposed adjacent to the folded portion. It has also been improved from the past, but there is still room for improvement.

  An object of the present invention is to solve the above-described problems, and the object of the present invention is to reduce the tire weight while allowing air to enter around the folded portion of the carcass ply. The object is to provide a pneumatic tire that can be suppressed.

The pneumatic tire according to the present invention includes a pair of bead cores, a main body portion continuously extending in a toroidal shape between the pair of bead cores, a continuous extension from the main body portion, and a periphery of the bead core. A carcass made of only one carcass ply provided with a folded portion that is wound from the inner side in the tire width direction to the outer side in the tire width direction, and the folded portion of the carcass ply includes: , Having a ply overlapping region extending along the main body portion of the carcass ply, and a tire radial length L1 from a tire radial inner end of the carcass ply to a tire radial inner end of the ply overlapping region, 4 to 45 mm, and the carcass ply cord constituting the carcass ply has a fineness per one of 5000 to 9100 dtex, And bending resistance characterized in that it is a 30～120MN.
According to the pneumatic tire of the present invention, it is possible to reduce the tire weight and suppress the air from entering around the folded portion of the carcass ply.

In the present specification, unless otherwise specified, each dimension such as “the length in the tire radial direction” is a case where the tire is assembled to a regular rim and the tire is filled with a regular internal pressure and is in an unloaded state. The dimension in the cross section in the tire width direction in is pointed out.
Here, “regular rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) JATMA YEAR BOOK, and in Europe, ETRTO (The European Tire and RIM Technical Organization's STANDARDDS MANUAL, TRA (The Tile and Rim Association, Inc.) YEAR BOOK OK, etc. Design Rim). “Regular internal pressure” refers to the air pressure corresponding to the maximum load capacity of a single wheel in the applicable size described in the above-mentioned standard.

In the pneumatic tire of the present invention, it is preferable that an outer bead filler is provided on the outer side in the tire width direction of the folded portion of the carcass ply, and the outer bead filler has a tire radial length L82 of 25 to 50 mm. .
Thereby, since the rigidity level | step difference in the bead core vicinity can be made loose, durability can be improved.

In the pneumatic tire of the present invention, the folded portion of the carcass ply is folded from the inner side in the tire width direction to the outer side in the tire width direction so as to wrap around the bead core and the end portion thereof is A tire radial direction outer end of the outer bead filler that is the ply overlapping region is located on a tire radial outer side of a tire radial direction outer end of the folded portion of the carcass ply, and a tire diameter of the folded portion of the carcass ply The direction length L5b is preferably 18 to 45 mm.
Thereby, while being able to reduce a weight of a tire more, generation | occurrence | production of the damage in the tire radial direction outer end of a folding | returning part can be suppressed.

In the pneumatic tire according to the present invention, the bead core is tapered on the outer side in the tire radial direction and between the main body portion of the carcass ply and the folded portion of the carcass ply toward the outer side in the tire radial direction in a sectional view in the tire width direction. It is preferable to further include an inner bead filler.
Thereby, since a rigidity level | step difference can be made moderate from a bead part to a sidewall part, durability can be improved.

In the pneumatic tire according to the present invention, a tire radial length L81 of the inner bead filler is 9 to 17 mm, and a folded portion of the carcass ply further includes a filler overlapping region extending along the inner bead filler. It is preferable that the tire radial direction length LPO of the ply overlapping region is 30 to 75% of the tire radial direction length L5b of the folded portion.
Thereby, in the ply overlapping region, a mooring action by a shearing force between the main body portion and the folded portion of the carcass ply can be generated, and the rolling resistance can be reduced while ensuring the durability of the carcass.

The pneumatic tire of this invention WHEREIN: It is suitable in the tire radial direction length L81 of the said inner bead filler being 30-45 mm.
Thereby, since a rigidity level | step difference can be made moderate from a bead part to a sidewall part, durability can be improved.

In the pneumatic tire according to the present invention, it is preferable that an adhesive layer is provided between the carcass ply cord and the covering rubber that covers the carcass ply cord.
Thereby, air entering between the carcass ply cord and the covering rubber can be suppressed.

In the pneumatic tire of the present invention, it is preferable that the elongation of the carcass ply cord at a load of 2 cN / dtex is 3.6 to 5.6%.
Thereby, the fatigue resistance and durability of the carcass ply and the vicinity thereof can be improved.

In the pneumatic tire of the present invention, it is preferable that the tensile strength at break of the carcass ply cord is 350 N or more.
Thereby, the fatigue resistance and durability of the carcass ply and the vicinity thereof can be improved.

In the pneumatic tire of the present invention, it is preferable that the twist coefficient per one filament bundle of the carcass ply cord is 0.34 to 0.63.
As a result, the entry of air around the folded portion of the carcass ply can be suppressed.

In the pneumatic tire of the present invention, it is preferable that the number of driving of the carcass ply cord into the carcass ply is 15 to 25 / 2.5 cm.
As a result, the entry of air around the folded portion of the carcass ply can be suppressed.

In the pneumatic tire of the present invention, it is preferable that the carcass ply cord includes a polyester fiber.
Thereby, weight reduction of a tire is attained.

In the pneumatic tire of the present invention, it is preferable that an adhesive layer is provided between the carcass ply cord and the covering rubber covering the carcass ply cord, and the adhesive forming the adhesive layer contains an isocyanate compound. It is.
Thereby, air entering between the carcass ply cord and the covering rubber can be suppressed.

  According to the present invention, it is possible to provide a pneumatic tire that can suppress the pneumatic entry around the folded portion of the carcass ply while allowing the weight of the tire to be reduced.

It is a tire width direction sectional view showing the important section of a 1st embodiment of the pneumatic tire of the present invention. 2A is a cross-sectional view of an example of the carcass ply, and FIG. 2B is a perspective view of the carcass ply cord of FIG. It is tire width direction sectional drawing which shows the principal part of 2nd Embodiment of the pneumatic tire of this invention. It is tire width direction sectional drawing which shows the principal part of 3rd Embodiment of the pneumatic tire of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
A first embodiment of a pneumatic tire according to the present invention (hereinafter sometimes simply referred to as “tire”) will be described with reference to FIGS. 1 and 2. The tire described in the present embodiment has a radial structure, and is particularly suitable for a pneumatic tire for heavy-duty vehicles such as trucks and buses. However, the tire of the present invention can also be applied to pneumatic tires used in other types of vehicles.
FIG. 1 is a cross-sectional view along the tire width direction showing the tire of the first embodiment. The tire of FIG. 1 has the same tire structure on both sides with respect to the tire equatorial plane C, so that only one side of the tire equatorial plane C is shown. The tire shown in FIG. 1 is a pneumatic tire for a heavy-duty vehicle. The tire is assembled to a regular rim and the tire is filled with a regular internal pressure and is in an unloaded state. ~ 350mm.

The tire shown in FIG. 1 is continuous from the tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction from both ends in the tire width direction of the tread portion 1, and from the sidewall portions 2 to the inside in the tire radial direction. It consists of a pair of bead parts 3. The tire includes a pair of bead cores 4 embedded in a pair of bead portions 3 and a carcass made of only one carcass ply 5 extending continuously between the pair of bead cores 4 in a toroidal shape. I have.
Since only one carcass ply 5 is provided, the weight of the tire can be reduced particularly by reducing the amount of rubber compared to a case where a plurality of carcass plies 5 are provided.

A belt 6 and a tread rubber 7 composed of a plurality of belt layers are sequentially arranged outside the crown region of the carcass ply 5 in the tread portion 1 in the tire radial direction. A tread pattern including a plurality of circumferential grooves 1a extending in the tire circumferential direction, for example, is formed on the tire outer surface of the tread rubber 7 constituting the tread surface.
An air-impermeable inner liner 9 is disposed on the side facing the tire lumen defined by a tire and a rim (not shown) (inner side of the tire).
The bead core 4 is formed in, for example, a substantially polygonal shape or a substantially circular shape (substantially square shape in the example of FIG. 1) in the tire width direction cross section by bundling a plurality of steel bead cords.

  2A and 2B are diagrams for explaining an example of the internal structure of the carcass ply 5 of FIG. As shown in the cross-sectional view of FIG. 2A, the carcass ply 5 includes a large number of carcass ply cords 51 arranged in a radial structure, and a covering rubber 52 that covers these carcass ply cords 51. As shown in the perspective view of FIG. 2B, the carcass ply cord 51 is composed of two filament bundles 510 formed by twisting a large number (for example, 500 pieces) of filaments 510a in the same direction. It is formed by twisting in the opposite direction. However, the carcass ply cord 51 may have another cord structure such as one in which one, two, or three or more filament bundles 510 are twisted.

  Returning to the cross-sectional view in the tire width direction of FIG. 1, the carcass ply 5 includes a main body portion 5 a continuously extending in a toroidal shape between the pair of bead cores 4, and a continuous extension from the main body portion 5 a. Is wrapped around from the inner side in the tire width direction to the outer side in the tire width direction and is turned back outward in the tire radial direction.

In the first embodiment, in the vicinity of the bead core 4, there are further rubber chafers 10, 11, chafer 20, and an outer bead filler 82 disposed on the outer side in the tire width direction from the folded portion 5 b of the carcass ply 5. , Provided. The rubber chafers 10 and 11, the chafer 20, and the outer bead filler 82 contribute to reducing the concentration of strain by relaxing the rigidity step from the bead portion 3 to the sidewall portion 2.
The rubber chafer 10 is disposed in the tire width direction inner side than the main body portion 5 a of the carcass ply 5 in the vicinity of the bead core 4, and is disposed further inward in the tire radial direction than the folded portion 5 b of the carcass ply 5. The chafer 20 covers the rubber chafer 10 from the side opposite to the carcass ply 5. The rubber chafer 11 is disposed on the outer side in the tire width direction from the folded portion 5b.
In the first embodiment, the outer bead filler 82 is disposed on the outer side in the tire width direction and the outer side in the tire radial direction from the folded-back portion 5 b and on the inner side in the tire width direction from the rubber chafer 11. The outer end in the tire radial direction of the outer bead filler 82 is located on the outer side in the tire radial direction with respect to the outer end in the tire radial direction of the folded portion 5b.
As will be described later with reference to FIGS. 3 and 4, in the present invention, the configuration of the folded portion 5 b when viewed in the cross section in the tire width direction can be different from that of the first embodiment.

In the first embodiment, the turn-up portion 5b of the carcass ply 5 is continuous from the inner side in the tire radial direction of the main body 5a so as to wrap the bead core 4 around the entire circumference of the bead core 4, and from the inner side in the tire width direction. It is wound outwardly in the tire width direction, and then folded back outward in the tire radial direction and further inward in the tire width direction. Further, the end portion of the folded portion 5 b extends along the main body portion 5 a on the outer side in the tire radial direction from the bead core 4. With this configuration, it is possible to suppress the occurrence of damage at the outer end in the tire radial direction of the turned-up portion, and the distortion of the portion (outer bead filler 82 or rubber chafer 11) mainly on the outer side in the tire width direction from the turned-up portion 5b. Concentration can be suppressed, and as a result, durability can be improved.
In 1st Embodiment, the bead filler is not provided between the main-body part 5a and the folding | returning part 5b. However, as will be described later with reference to FIGS. 3 and 4, in the present invention, an inner bead filler positioned between the main body portion 5 a and the folded portion 5 b may be provided.

In the present specification, a portion of the folded portion 5b that extends along the main body 5a is referred to as a “ply overlap region PO”. The carcass ply cord 51 in the ply overlapping region PO of the folded portion 5b extends from the carcass ply cord 51 of the main body portion 5a with a substantially constant interval.
In the present invention, the folded portion 5b of the carcass ply 5 has the ply overlap region PO. For example, in the first embodiment, the end portion of the folded portion 5b that is located on the outer side in the tire radial direction from the bead core 4 is the ply overlap region PO.

In the present invention, the tire radial direction length L1 from the tire radial direction inner end of the carcass ply 5 to the tire radial direction inner end of the ply overlap region PO is 4 to 45 mm.
In the present invention, the tire radial direction length L1 from the inner radial end of the carcass ply 5 to the inner radial end of the ply overlap region PO is shorter than that of the conventional tire. By setting the length L1 in the tire radial direction in this way, it is possible to suppress the occurrence of damage at the outer end in the tire radial direction of the folded portion, and mainly the portion outside the tire width direction (outer bead filler) from the folded portion 5b. 82 and the rubber chafer 11) can suppress the concentration of strain, and as a result, the durability can be improved.
In the first embodiment shown in FIG. 1, the tire radial direction inner end of the ply overlap region PO is adjacent to the bead core 4, and the tire radial direction of the ply overlap region PO from the tire radial inner end of the carcass ply 5. 4-9 mm is suitable for the tire radial direction length L1 to an inner side end.

In the present invention, the carcass ply cord 51 constituting the carcass ply 5 has a fineness of 5000 to 9100 dtex (decitex).
Here, the fineness in units of dtex refers to the number of grams of mass per 10,000 m in length.
In the example of FIG. 2, since the carcass ply cord 51 is formed by two strands of the filament bundle 510, twice the fineness per filament bundle 510 is the fineness per one of the carcass ply cord 51. Equivalent to.
The carcass ply cord 51 of the tire of the present invention has higher fineness than the carcass ply cord used in a conventional tire including a plurality of carcass plies. When the material of the carcass ply cord is the same, the fineness of the carcass ply cord can be seen as a measure of the cord diameter of the carcass ply cord. Therefore, it can be said that the carcass ply cord 51 of the tire of the present invention has a larger cord diameter than the carcass ply cord used in the conventional tire. In the present invention, since the fineness of the carcass ply cord 51 is large (the cord diameter is large), the number of carcass plies is reduced to one from the viewpoint of reducing the weight of the tire, and the function of the carcass (suppression of excessive deformation of the tire) Functions and the function of maintaining the internal pressure of the tire).

In the present invention, the carcass ply cord 51 constituting the carcass ply 5 has a bending resistance of 30 to 120 mN.
Here, the bending resistance is a scale representing bend resilience, and by extension, can be said to be a scale representing bendability. The measuring method will be described later.
By making the bending resistance of the carcass ply cord 51 of the tire of the present invention relatively low at 120 mN or less, the carcass ply cord 51 can be easily bent. As will be described later, the bending resistance of the carcass ply cord can be adjusted by adjusting the configuration (twisting method and material) of the carcass ply cord and the manufacturing method.
By lowering the bending resistance of the carcass ply cord 51, the bending resistance of the unvulcanized carcass ply (treat) itself, which is used during the production of the green tire to form the carcass ply 5, is reduced accordingly. be able to. Here, the unvulcanized carcass ply is a belt-like member formed by coating a large number of carcass ply cords 51 with unvulcanized rubber. Therefore, when a raw tire is manufactured, when an unvulcanized carcass ply is folded around the bead core on the green tire molding drum to form a folded portion of the unvulcanized carcass ply, for example, with a small bending radius. Even if it tries to bend, it can be bent as expected. Therefore, in the finally completed tire, the air between the folded portion 5b of the carcass ply 5 and the tire constituent portion (the outer bead filler 82, the bead core 4 or the main body portion 5a of the carcass ply 5) disposed adjacent thereto. Can remain (air entering).
Particularly, in the present invention, as described above, from the viewpoint of improving durability, the tire radial direction length L1 from the tire radial direction inner end of the carcass ply 5 to the tire radial direction inner end of the ply overlapping region PO is set to 4 to 45 mm. Since it is relatively short, it is often necessary to bend the unvulcanized carcass ply with a small bending radius during the production of the green tire. Therefore, it is significant to set the bending resistance of the carcass ply cord 51 as described above.
In addition, by setting the bending resistance of the carcass ply cord 51 of the tire of the present invention to 30 mN or more, the carcass function can be sufficiently exhibited.

ここに、Ｂ_r：剛軟度（ｍＮ）
ＲＧ：試験片が振り子から離れるときの目盛
ａ、ｂ、ｃ：荷重取付孔と支点間の距離（ｍｍ）
Ｗ_a（ｇ）、Ｗ_b（ｇ）、Ｗ_c：荷重取付孔に取り付けたおもりの質量（ｇ）
Ｌ：試験片の長さ（ｍｍ）
ｄ：試験片の幅（すなわちコード径）（ｍｍ） Here, a method for measuring the bending resistance of the carcass ply cord 51 will be described. In the present invention, the bending resistance of the carcass ply cord 51 is measured in accordance with the provisions of “8.22.1 A bending resistance (Gurley method)” of JIS L 1096 (2010).
First, five test pieces having a length of Lmm are collected from the carcass ply cord 51 to be measured.
Using a Gurley type testing machine (for example, Garlace Tefness Tester manufactured by Toyo Seiki Seisakusho Co., Ltd.), attach the test piece to the chuck and adjust it to one of the scales 1, 1.5 and 2 (L / 25.4) on the movable arm. The chuck is fixed and the specimen is moved away from the top of the pendulum. Next, weights W _a (g), W _b (g), and W _c (g) are attached individually or in combination from the fulcrum of the pendulum to the lower load mounting holes a, b, and c, and in _a vertical state without vibration To. Here, the movable arm is moved to the right or left at a constant speed at a speed of 2 times / min. Read the scale RG when the lower part of the specimen touches the pendulum and leaves the pendulum. The bending resistance is measured on the front and back of each of five test pieces. 5 times to calculate an average value, by the following equation to determine the stiffness B _r. Round to one decimal place.

Here, B _r : Bending softness (mN)
RG: Scale when the test piece is separated from the pendulum a, b, c: Distance between load mounting hole and fulcrum (mm)
W _a (g), W _b (g), W _c : Mass of weight attached to load mounting hole (g)
L: Length of test piece (mm)
d: Specimen width (ie, cord diameter) (mm)

Returning to FIG. 1, in the first embodiment, it is preferable that the length L82 of the outer bead filler 82 in the tire radial direction is 25 to 50 mm.
Thereby, since the rigidity level | step difference in the bead core vicinity can be made loose, durability can be improved.

Moreover, in 1st Embodiment, it is suitable in the tire radial direction length L5b of the folding | returning part 5b of the carcass ply 5 being 18-45 mm.
Thereby, generation | occurrence | production of the damage in the tire radial direction outer end of a folding | returning part can be suppressed.

Moreover, in 1st Embodiment, it is suitable in the tire radial direction length LPO of the ply overlap area | region PO of the folding | turning part 5b being 14-36 mm.
Forces in directions opposite to each other are generated in the main body portion 5a and the turn-up portion 5b in the ply overlapping region PO, and by setting the length LPO in the tire radial direction of the ply overlapping region PO in this way, the overlapping is achieved. Appropriate forces in the opposite directions can be generated in the region PO, and consequently, the force applied to the outermost end portion in the tire radial direction of the folded portion 5b can be reduced, and the durability of the bead portion 3 is increased. Can do.

In the tire of the present invention, as shown in FIG. 2A, it is preferable that an adhesive layer 53 is provided between the carcass ply cord 51 and the covering rubber 52 that covers the carcass ply cord 51. .
Thereby, since the adhesiveness between the carcass ply cord 51 and the covering rubber 52 is enhanced, the entry of air between the carcass ply cord 51 and the covering rubber 52 can be suppressed.
In order to form the adhesive layer 53, for example, when manufacturing an unvulcanized carcass ply, a large number of carcass ply cords 51 hung in a comb shape are filled with an adhesive as a material of the adhesive layer 53. The carcass ply cord 51 put out in the adhesive pool (DIP process), dried from the adhesive pool (drying process), and then covered with unvulcanized rubber (calendar process) may be used.

In the drying process after the DIP process, the carcass ply cord 51 is heated to a temperature of 230 to 250 ° C. while the carcass ply cord 51 is heated to 1.0 × 10 ^{−3 to} 2.0 × 10 ⁻³ N / It is preferable to apply dtex tension. Thereby, the carcass ply cord 51 which is easy to bend can be generated.

In the tire of the present invention, it is preferable that the elongation of the carcass ply cord 51 at 2 cN / dtex tensile load is 3.6 to 5.6%.
Since this value is lower than that of the conventional tire, it indicates that the carcass ply cord 51 is less likely to extend with respect to the tensile load than in the past. According to this configuration, since distortion around the carcass ply 5 can be reduced, the fatigue resistance and durability of the carcass ply 5 and its vicinity can be improved. In the tire of the present invention, since the fineness of the carcass ply cord 51 is high as described above, it is possible to make the carcass ply cord 51 more difficult to extend than in the past.
The elongation of the carcass ply cord 51 at 2 cN / dtex tensile load is the elongation S obtained in accordance with the provisions of “8.5 Tensile Strength and Elongation 8.5.1 Standard Time Test” of JIS L 1013 (2010). Point to.

In the tire of the present invention, it is preferable that the tensile strength at break of the carcass ply cord 51 is 350 N or more.
Since this value is higher than that of the conventional tire, it indicates that the carcass ply cord 51 is less likely to break with respect to the tensile load than the conventional tire. According to this configuration, the fatigue resistance and durability of the carcass ply 5 and its vicinity can be improved.
In addition, the tensile breaking strength of the carcass ply cord 51 is a tensile test for one carcass ply cord 51 in accordance with the provisions of “8.5 Tensile Strength and Elongation 8.5.1 Standard Time Test” of JIS L 1013 (2010). Is the strength SD (N) when the carcass ply cord 51 is cut.

ここで、Ｔは、１本のカーカスプライコード５１を構成するフィラメント束５１０の上撚りの回数(回／１０ｃｍ)であり、Ｄは、１本のカーカスプライコード５１の繊度（ｄｔｅｘ）の半分であり、ρは、カーカスプライコード５１を構成するコード材料の比重である。
この構成により、カーカスプライコード５１を曲げ易くすることができ、ひいては、カーカスプライ５の折り返し部５ｂの周りでのエア入りを抑制できる。 In the tire of the present invention, it is preferable that the twist coefficient per one filament bundle 510 of the carcass ply cord 51 is 0.34 to 0.63. Here, the twist coefficient is obtained by the following equation.

Here, T is the number of twists of the filament bundle 510 constituting one carcass ply cord 51 (times / 10 cm), and D is half the fineness (dtex) of one carcass ply cord 51. Yes, ρ is the specific gravity of the cord material constituting the carcass ply cord 51.
With this configuration, the carcass ply cord 51 can be easily bent, and as a result, entry of air around the folded portion 5b of the carcass ply 5 can be suppressed.

In the tire of the present invention, it is preferable that the number of driving of the carcass ply cord 51 into the carcass ply 5 is 15 to 25 / 2.5 cm.
With this configuration, the carcass ply cord 51 can be easily bent, and as a result, entry of air around the folded portion 5b of the carcass ply 5 can be suppressed.

In the tire of the present invention, it is preferable that the carcass ply cord 51 includes polyester fiber.
Thereby, weight reduction of a tire is attained.
However, the cord material of the carcass ply cord 51 may be any resin other than polyester, or may be a metal such as steel.

In the tire of the present invention, when the adhesive layer 53 is provided between the carcass ply cord 51 and the covering rubber 52 as in the example of FIG. 2, the adhesive that forms the adhesive layer 53 contains an isocyanate compound. Is preferable.
Thereby, since the adhesiveness between the carcass ply cord 51 and the covering rubber 52 is enhanced, the entry of air between the carcass ply cord 51 and the covering rubber 52 can be suppressed.

[Second Embodiment]
Next, with reference to FIG. 3, a second embodiment of the tire of the present invention will be described focusing on differences from the first embodiment. The tire according to the second embodiment shown in FIG. 3 differs from the tire according to the first embodiment mainly in the configuration of the folded portion 5b of the carcass ply 5 when viewed in a cross section in the tire width direction. 5 in that an inner bead filler is provided between the body portion 5a and the folded portion 5b. The internal structure of the carcass ply 5 such as the fineness and bending resistance of the carcass ply cord 51 and the twisted structure of the carcass ply cord 51 are the same as those described in the first embodiment.

In the second embodiment, in the tire width direction cross-sectional view, the inner side of the bead core 4 is tapered toward the outer side in the tire radial direction between the main body part 5a and the folded part 5b of the carcass ply 5 in the tire radial direction outer side. A bead filler 81 is further provided.
Thereby, since a rigidity level | step difference can be made moderate from the bead part 3 to the sidewall part 2, durability can be improved.

  In the second embodiment, the turn-up portion 5b of the carcass ply 5 further includes a filler overlapping region FO extending along the inner bead filler 81, and the ply is disposed on the outer side in the tire radial direction from the filler overlapping region FO. It has an overlap region PO.

  In the second embodiment, the outer bead filler 82 is disposed on the outer side in the tire width direction from the main body portion 5a, on the outer side in the tire width direction and on the outer side in the tire radial direction from the folded portion 5b, and on the inner side in the tire width direction from the rubber chafer 11. ing. The outer end in the tire radial direction of the outer bead filler 82 is located on the outer side in the tire radial direction with respect to the outer end in the tire radial direction of the folded portion 5b.

In 2nd Embodiment, it is suitable in the tire radial direction length L81 of the inner side bead filler 81 being 9-17 mm.
In the second embodiment, it is preferable that the tire radial direction length LPO of the ply overlap region PO is 30 to 75% of the tire radial direction length L5b of the folded portion 5b.
Thereby, in the ply overlap region PO, a mooring action due to the shearing force between the main body portion 5a and the folded portion 5b of the carcass ply 5 can be generated, and the rolling resistance is reduced while ensuring the durability of the carcass ply 5. Can do.
Moreover, in 2nd Embodiment, it is suitable in the tire radial direction length L5b of the folding | returning part 5b of the carcass ply 5 being 22-64 mm. Further, it is preferable that the tire radial direction length LPO of the ply overlap region PO is 9 to 38 mm.

  In the second embodiment shown in FIG. 2, the tire radial direction length L1 from the inner radial end of the carcass ply 5 to the inner radial end of the ply overlapping region PO is preferably 13 to 26 mm.

Moreover, in 2nd Embodiment, it is suitable in the tire radial direction length L82 of the outer side bead filler 82 being 25-50 mm.
Thereby, since the rigidity level | step difference in the bead core vicinity can be made loose, durability can be improved.

[Third Embodiment]
Next, a third embodiment of the tire of the present invention will be described with reference to FIG. 4 with a focus on differences from the second embodiment. In the tire according to the third embodiment shown in FIG. 4, the inner bead filler 81 is provided between the main body 5a and the folded portion 5b of the carcass ply 5, and the folded portion 5b of the carcass ply 5 is a filler overlapping region. In the point which has FO, it is the same as that of the tire of 2nd Embodiment. However, the tire of the third embodiment is mainly different in the configuration of the folded portion 5b of the carcass ply 5 and the dimensions of the inner bead filler 81 and the outer bead filler 82 when viewed in the tire width direction cross section. The internal structure of the carcass ply 5 such as the fineness and bending resistance of the carcass ply cord 51 and the twisted structure of the carcass ply cord 51 are the same as those described in the first embodiment.

In 3rd Embodiment, the tire radial direction outer side end of the folding | returning part 5b of the carcass ply 5 is located in the tire width direction outer side rather than the tire maximum width position MWH.
And in 3rd Embodiment, the folding | returning part 5b of the carcass ply 5 has the ply overlap area | region PO in the tire radial direction outer side from the filler overlap area | region FO.

  In the third embodiment, the outer bead filler 82 is disposed on the outer side in the tire width direction from the folded portion 5 b and on the inner side in the tire width direction from the rubber chafer 11. The outer end in the tire radial direction of the folded portion 5b is located on the outer side in the tire radial direction with respect to the outer end in the tire radial direction of the outer bead filler 82.

In 3rd Embodiment, the tire radial direction length L81 of the inner side bead filler 81 is preferable in it being 30-45 mm, and it is more preferable in it being 30-40 mm.
Thereby, since a rigidity level | step difference can be made moderate from the bead part 3 to the sidewall part 2, durability can be improved.

  Moreover, in 3rd Embodiment shown in FIG. 3, 33-45 mm of tire radial direction length L1 from the tire radial direction inner side end of the carcass ply 5 to the tire radial direction inner side end of the ply overlap area | region PO is suitable.

In the third embodiment, the tire radial direction length L82 of the outer bead filler 82 is shorter than the tire radial direction length L81 of the inner bead filler 81.
In 3rd Embodiment, it is suitable in the tire radial direction length L82 of the outer side bead filler 82 being 25-50 mm.
Thereby, since the rigidity level | step difference in the bead core vicinity can be made loose, durability can be improved.

Moreover, in 3rd Embodiment, it is suitable in the tire radial direction length LPO of the ply overlap area | region PO being 46-81 mm.
Thereby, it is possible to generate a sufficient reaction force between the main body portion 5a and the turn-up portion 5b in the ply overlap region PO, and consequently reduce the force applied to the outermost end portion in the tire radial direction of the turn-up portion 5b. In addition to this, it is possible to prevent trauma such as a side cut that easily occurs in a tire having a high tire cross-section height H as in this example.
In addition, it is suitable in the tire radial direction length L5b of the folding | returning part 5b that it is 79-126 mm.

  As described above, as described in the first to third embodiments, according to the tire of the present invention, the weight of the tire can be reduced, and the rolling resistance of the tire can be reduced. Can be prevented from entering the air.

In order to confirm the effect of the present invention, comparative tires 1 to 4 and example tires 1 to 6 were prototyped and evaluated, respectively. The internal structure of each tire was different only in the points shown in Table 1. Each tire is a pneumatic tire for heavy-duty vehicles, and has a tire size of LT225 / 75R16, a rim size of 16 / 6J (JATMA standard rim), and a tire cross-section height H of 210 mm. In Table 1, “the fineness of the cord (dtex)” and “the stiffness of the cord (mN)” respectively indicate the fineness and the stiffness of the carcass ply cord described above.
The comparative tire 1 was provided with two carcass plies, and the fineness per carcass ply cord of each carcass ply was 3340 dtex. The comparative tires 2 to 4 and the example tires 1 to 6 were provided with only one carcass ply, and the fineness per one carcass ply cord was 6680 dtex.
And about each tire, each tire weight was measured and the measured value was converted into the relative index | exponent. Further, for each tire, it was evaluated whether or not air entry occurred between the folded portion of the carcass ply and the tire constituent portion disposed adjacent thereto. The results were as shown in Table 1.

  As can be seen from Table 1, in Example tires 1 to 6, unlike Comparative Examples tires 1 to 4, it was possible to prevent air from entering around the folded portion of the carcass ply while reducing the weight of the tire.

  The present invention can be used for various pneumatic tires including pneumatic tires for heavy-duty vehicles such as trucks and buses.

DESCRIPTION OF SYMBOLS 1: Tread part, 1a: Circumferential groove, 2: Side wall part, 3: Bead part, 4: Bead core, 5: Carcass ply (carcass), 5a: Main-body part, 5b: Folding part, 6: Belt, 7: Tread Rubber: 9: Inner liner, 10, 11: Rubber chafer, 20: Chafer, 51: Carcass ply cord, 52: Covered rubber, 53: Adhesive layer, 81: Inner bead filler, 82: Outer bead filler, 510: Filament bundle, 510a: Filament, C: Tire equatorial plane, FO: Filler overlap area, H: Tire cross-section height, MWH: Maximum width position of tire, PO: Ply overlap area

Claims (13)

A pair of bead cores,
A main body portion continuously extending in a toroidal shape between the pair of bead cores, and continuously extending from the main body portion, and is wrapped around the bead core from the inner side in the tire width direction to the outer side in the tire width direction. A carcass composed of only one carcass ply provided with a folded portion,
A pneumatic tire comprising:
The folded portion of the carcass ply has a ply overlap region extending along the main body of the carcass ply;
The tire radial direction length L1 from the tire radial inner end of the carcass ply to the tire radial inner end of the ply overlapping region is 4 to 45 mm,
A pneumatic tire characterized in that the carcass ply cord constituting the carcass ply has a fineness of 5000 to 9100 dtex and a bending resistance of 30 to 120 mN. On the outer side in the tire width direction of the folded portion of the carcass ply, an outer bead filler is provided,
The pneumatic tire according to claim 1, wherein the outer bead filler has a tire radial direction length L82 of 25 to 50 mm. The folded portion of the carcass ply is wrapped around the bead core so as to wrap the bead core from the tire width direction inner side to the tire width direction outer side, and the end portion thereof is the ply overlapping region,
The tire radial direction outer end of the outer bead filler is located on the tire radial direction outer side than the tire radial direction outer end of the folded portion of the carcass ply,
The pneumatic tire according to claim 2, wherein a tire radial direction length L5b of the turned-up portion of the carcass ply is 18 to 45 mm.   An inner bead filler that is tapered toward the outer side in the tire radial direction in a cross-sectional view in the tire width direction between the main body portion of the carcass ply and the folded portion of the carcass ply on the outer side in the tire radial direction of the bead core; The pneumatic tire according to claim 1, wherein the pneumatic tire is provided. A tire radial direction length L81 of the inner bead filler is 9 to 17 mm,
The folded portion of the carcass ply further has a filler overlap region extending along the inner bead filler;
The pneumatic tire according to claim 4, wherein a tire radial direction length LPO of the ply overlapping region is 30 to 75% of a tire radial direction length L5b of the folded portion.   The pneumatic tire according to claim 4, wherein a tire radial length L81 of the inner bead filler is 30 to 45 mm.   The pneumatic tire according to any one of claims 1 to 6, further comprising an adhesive layer between the carcass ply cord and a covering rubber that covers the carcass ply cord.   The pneumatic tire according to any one of claims 1 to 7, wherein an elongation of the carcass ply cord at a load of 2 cN / dtex is 3.6 to 5.6%.   The pneumatic tire according to any one of claims 1 to 8, wherein a tensile breaking strength of the carcass ply cord is 350 N or more.   The pneumatic tire according to any one of claims 1 to 9, wherein a twist coefficient per filament bundle of the carcass ply cord is 0.34 to 0.63.   The pneumatic tire according to any one of claims 1 to 10, wherein the number of driving of the carcass ply cord into the carcass ply is 15 to 25 / 2.5 cm.   The pneumatic tire according to any one of claims 1 to 11, wherein the carcass ply cord includes a polyester fiber. Having an adhesive layer between the carcass ply cord and the covering rubber covering the carcass ply cord;
The pneumatic tire according to claim 1, wherein the adhesive forming the adhesive layer includes an isocyanate compound.

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