JP5028896B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that prevents a bead core from collapsing in cross-section during tire vulcanization and enhances fitting with a rim.

  As a bead core embedded in a bead portion of a pneumatic tire, steel wires arranged in a width direction and wound in a radial direction to be formed into an annular grommet are widely used. In general, the bead core plays a role of locking both ends of the carcass layer forming the skeleton of the tire and improving the fit between the tire and the rim to prevent leakage of tire internal pressure.

Therefore, conventionally, a lapping material has been spirally wound around the grommet so that the function of the bead core wire that controls the function is not lost due to scattering (for example, patents). Reference 1). However, in the conventional wrapping material, there is a limit to the grommet bundling properties, and when the carcass layer is subjected to a strong tensile force at the time of expansion in the vulcanization process of the tire, as shown in FIG. Since the cross-sectional shape of the laminated wires is collapsed, and the tightening force of the bead core in the vulcanized tire is reduced, there is a problem that the fitting property with the rim is deteriorated.
JP-A-8-169216

  An object of the present invention is to solve such a conventional problem, and to provide a pneumatic tire that prevents the bead core from being deformed in cross-sectional shape in a vulcanized tire and improves the fitting property with a rim. There is to do.

In order to achieve the above object, the pneumatic tire according to the present invention is formed by arranging rubber-coated steel wires in the width direction and winding them so as to be laminated in the radial direction to form an annular grommet, and surrounding the grommet. In a pneumatic tire in which a bead core in which a wrapping material is spirally wound is embedded in a pair of left and right bead portions, and both ends of a carcass layer are folded around the bead core from the inside to the outside of the tire, the wrapping material is 150 ° C. A cord or monofilament comprising an aliphatic polyketone fiber represented by the following formulas (1) and (2) having a shrinkage stress during dry heat of 0.40 to 0.80 cN / dtex and a thickness of 1100 to 2750 dtex in conjunction with constructing, when configuring the encoding said wrapping material, multifilament the code As twisted cord, the number of twists per 10cm, characterized in that the 20 to 40.
_{- (CH 2 -CH 2 -CO)} n - (R-CO) m - ······ (1)
(Where R is an alkylene group having 3 or more carbon atoms)
1.00 ≦ (n + m) /n≦1.05 (2)

Furthermore, in the above-described configuration, it is preferable to configure as described in the following (A) and / or (B) .
(A) The winding pitch of the wrapping material is set to 5 to 30 mm.
(B) A plurality of cords or monofilaments are arranged in parallel to form a rubber-coated belt-like body, and the belt-like body is spirally wound around the grommet.

According to the present invention, since the wrapping material wound around the grommet is composed of cords or monofilaments made of aliphatic polyketone fibers having high heat shrinkage stress, the binding force against the grommet by the wrapping material is increased in the tire vulcanization process. Thus, even when a strong tensile force is applied from the carcass layer at the time of expansion, the bead core cross-section can be prevented from being deformed, and the fit between the bead portion and the rim can be improved.
In addition, since the shrinkage stress at the time of dry heat of the cord or monofilament constituting the wrapping material is set to 0.40 to 0.80 cN / dtex, the binding force of the grommet can be surely increased. Alternatively, since the thickness of the monofilament is set to 1100 to 2750 dtex, the binding force of the grommet can be more reliably ensured while suppressing the interference with the carcass layer.
And when this wrapping material is constituted by a cord, the cord is constituted by a multifilament twisted cord and the number of twists per 10 cm in this cord is set to 20 to 40, so that the fatigue resistance of the cord is lowered. Without this, it is possible to suppress the elongation of the cord, and to easily adjust the tension during the lapping process.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a half sectional view showing a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a part of a bead core in the tire of FIG.

  In FIG. 1, a pneumatic tire 1 has bead cores 3 and 3 embedded in a pair of left and right bead portions 2 and 2, and both end portions 4 a and 4 a of a carcass layer 4 are placed around the left and right bead cores 3 and 3 from the inside of the tire. Folds outward.

As shown in FIG. 2, the left and right bead cores 3 are formed of annular grommet 3 w in which rubber-coated steel wires w are arranged in the width direction and wound so as to be laminated in the radial direction. A wrapping material 5 made of a cord or monofilament composed of an aliphatic polyketone fiber (hereinafter referred to as POK fiber) represented by 1) and (2) is spirally wound.
— (CH ₂ —CH ₂ —CO) _n — (R—CO) _m — (1)
(Where R is an alkylene group having 3 or more carbon atoms)
1.00 ≦ (n + m) /n≦1.05 (2)

  Thus, by wrapping the cord or monofilament made of POK fiber having a high heat shrinkage stress as the wrapping material 5 around the grommet 3w, the binding force on the grommet 3w by the wrapping material 5 during tire vulcanization is increased. Even when a strong tensile force is applied from the carcass layer 4 at the time of expansion, it is possible to prevent the cross-section of the bead core 3 from being deformed and to improve the fit between the bead portion 2 and the rim.

  In addition, the winding pitch of the wrapping material 5 wound around the grommet 3w is not particularly limited, but may be adjusted so that the winding pitch P shown in FIG. 2 is 5 to 30 mm. Thereby, shape collapse of bead core 3 can be prevented efficiently.

In the present invention , the cord or monofilament constituting the wrapping material 5 has a shrinkage stress of 0 . 40 to 0.80 cN / dtex POK fiber is used . Thereby, the binding force of the grommet 3w can be reliably increased. Here, the shrinkage stress at the time of dry heat at 150 ° C. mentioned above refers to a value when measured according to JISL1017.

  The cord or monofilament described above is preferably subjected to an adhesive treatment by a known means in advance in order to improve the adhesion with rubber, and is wound around the grommet 3w. If necessary, the surface of the cord or monofilament may be covered with rubber, and this may be wound around the grommet 3w.

Furthermore, in the present invention, the thickness of the cord or monofilament is set to 1100-2750 dtex . If the thickness is less than 1100 d tex, the binding force of the grommet 3 w will be insufficient, and if it exceeds 2750 dtex, the cord diameter will be too thick and interfere with the carcass layer 4.

Furthermore, in the present invention, when the wrapping material 5 described above is constituted by a cord, the cord is constituted by a multifilament twisted cord, and the number of twists per 10 cm of the cord is set to 20-40 . If the number of twists per 10 cm is less than 20 , the fatigue resistance of the cord will decrease, and if it exceeds 40 , the elongation of the cord will be too large, and it will be difficult to adjust the tension during lapping.

  In the present invention, a plurality of the cords or monofilaments described above may be arranged in parallel and formed into a rubber-coated belt-like body, and this belt-like body may be spirally wound around the grommet 3w. The winding pitch of the strip in this case is not particularly limited, but the strip may be wound so that the number of cords or monofilaments per unit length of the grommet 3w is the same as the above.

As described above, the pneumatic tire of the present invention uses a bead core using a cord or monofilament having a thickness of 1100 to 2750 dtex made of POK fiber having high heat shrinkage stress as a wrapping material spirally wound around a grommet. In addition, when the wrapping material is composed of a cord, the number of twists per 10 cm is set to 20 to 40, and this is embedded in the left and right bead parts, so that the grommet binding property at the time of vulcanization This improves the fit of the bead core and prevents the bead core from collapsing in cross section. It has a simple structure and has excellent effects, so various tires including passenger car tires are available. Can be widely applied to.

  A tire of the present invention (Example) and comparative tires (Comparative Examples 1 to 3) in which the cord shown in Table 1 is wound as a wrapping material in a bead core embedded in the left and right bead portions, with a tire size of 225 / 45R17 and a tire structure as shown in FIG. ) Were prepared. In each tire, the structure of the grommet constituting the bead core was 6 + 6 + 6 + 6 + 5, and the wire diameter of the steel wire was 1.2 mm.

About these four types of tires, the following test method was used to observe the change in the cross-sectional shape of the bead core after vulcanization, and the fitting property with the rim was evaluated. The results are also shown in Table 1.
[Changes in cross-sectional shape of bead core after vulcanization]
The bead portion of the tire after vulcanization is cut, and the change in the cross-sectional shape of the bead core (referred to as “shape change before and after vulcanization” in Table 1) is observed, and the result is A (no change), B (somewhat) The results are shown in Table 1 in three stages of (with change) and C (large change).
[Matchability with rim]
Using a jig that concentrically pushes the tire bead part, the reaction force received from the tire bead part when the jig is enlarged concentrically (the product of the pressure and contact area the jig receives from the bead part = tire fitting The resultant force was measured to evaluate the fit with the rim, and the results were displayed in Table 1 in four stages: A (excellent), B (good), C (inferior), and D (very inferior). .

  From the results shown in Table 1, the tire of the present invention using the POK fiber cord as the wrapping material does not show a collapse in the bead core in the vulcanized tire and improves the fitting property with the rim, as compared with the comparative tire. You can see that

1 is a half sectional view showing a pneumatic tire according to an embodiment of the present invention. It is a perspective view which shows a part of bead core in the tire of FIG. It is a photograph which shows the cross section of the bead part in the conventional vulcanized tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Bead core 3w Grommet 4 Carcass layer 5 Wrapping material w Steel wire

Claims (3)

The rubber-coated steel wires are arranged in the width direction, and are wound to be laminated in the radial direction to form an annular grommet, and a bead core in which a wrapping material is spirally wound around the grommet is a pair of left and right bead portions. Embedded in the pneumatic tire in which both ends of the carcass layer are folded around the bead core from the inside to the outside of the tire,
Aliphatic polyketone represented by the following formulas (1) and (2) wherein the wrapping material has a shrinkage stress of 0.40 to 0.80 cN / dtex at dry heat at 150 ° C. and a thickness of 1100 to 2750 dtex. A pneumatic tire in which a cord or monofilament made of fiber is used, and when the wrapping material is made of a cord, the cord is a multifilament twisted cord and the number of twists per 10 cm is 20 to 40 .
_{- (CH 2 -CH 2 -CO)} n - (R-CO) m - ······ (1)
(Where R is an alkylene group having 3 or more carbon atoms)
1.00 ≦ (n + m) /n≦1.05 (2) The pneumatic tire according to claim 1, wherein a winding pitch of the wrapping material is 5 to 30 mm. The pneumatic tire according to claim 1 or 2, wherein a plurality of the cords or monofilaments are arranged in parallel to form a belt-like body covered with rubber, and the belt-like body is spirally wound around the grommet.

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