JP2009226995A - Bead core for pneumatic tire, pneumatic tire, and manufacturing method of the pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire wherein change in RFV after rim assembly is suppressed to the minimum by improving rim assembling properties of the tire. <P>SOLUTION: The pneumatic tire 1 is formed by embedding an annular bead core 7 formed by continuously winding one or more bead wire 9 in a bead part 5. The bead wire 9 is shaped to a radius of curvature R within a range of 0.05D or more and less than 0.45D with respect to a rim diameter D of a standard rim 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bead core for a pneumatic tire formed by annularly winding one or more bead wires, a pneumatic tire in which such a bead core is embedded in a bead portion, and a method for manufacturing such a pneumatic tire. In particular, to improve the rim assembly of a pneumatic tire.

  In general, in a pneumatic tire, an annular bead core formed by continuously winding a bead wire is embedded in a bead portion, thereby fitting the tire to a rim. It is known that the fitting pressure and bead unseating resistance are greatly affected by the rigidity of the bead core (see, for example, Patent Document 1). Increasing the amount of the bead wire constituting the bead core to increase the rigidity of the bead core can increase the bead unseating resistance, but this also causes an increase in fitting pressure. On the other hand, when the use amount of the bead wire constituting the bead core is reduced, the fitting pressure is lowered, but at the same time, there is a problem that the bead unseating resistance value is also lowered. Thus, it has been difficult to improve both the fitting pressure and the bead seating resistance value and improve the overall fitting characteristics.

  In order to improve such fitting characteristics, Patent Document 2 discloses that a bead wire constituting a bead core is continuously brazed with a radius of curvature R ′ of 0.60R to 1.10R with respect to the inner diameter 2R of the bead core. Is described.

Japanese Patent Laid-Open No. 2001-233023 JP 2007-302153 A

  However, in the technique described in Patent Document 2, the rim assembly is not improved, the fitting of the tire to the rim is insufficient, and the rim assembly is compared with the RFV (radial fall variation) level of the tire alone. Later RFV sometimes worsened.

  Accordingly, an object of the present invention is to solve these problems of the prior art, and the object is to minimize the amount of change in RFV after rim assembly by optimizing the rigidity of the bead wire. It is an object of the present invention to provide a pneumatic tire that can be suppressed to a limit and that has improved tire rim assembly.

  In order to achieve the above object, a bead core for a pneumatic tire according to the present invention is formed into an annular shape by continuously winding one or more bead wires, and the bead wire is formed of a standard rim. It is brazed with a radius of curvature R in the range of 0.05D or more and less than 0.45D with respect to the rim diameter D.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire in which an annular bead core formed by continuously winding one or more bead wires is embedded in a bead portion. The bead wire is characterized by being brazed with a radius of curvature R in the range of 0.05 D or more and less than 0.45 D with respect to the rim diameter D of the standard rim.

  Furthermore, in order to achieve the above object, a pneumatic tire manufacturing method according to the present invention is a pneumatic tire manufacturing method in which an annular bead core is embedded in a bead portion, and is 0 with respect to a rim diameter D of a standard rim. The bead core is formed by continuously winding one or more bead wires brazed with a radius of curvature R in the range of .05D to less than 0.45D.

  The “standard rim” used here is a standard rim (JATMA, TRA, ETRTO, etc.) for an applicable size specified in industrial standards and standards effective in the area where the tire is manufactured, sold, or used. Or “Approved Rim”, “Recommended Rim”).

  Moreover, the curvature radius of the brazing of the bead wire embedded in the pneumatic tire is specified by the following procedure. That is, after disassembling the tire and taking out the bead core so as not to damage the bead wire, the bead wire for two weeks is cut out from the end of the bead wire arranged on the outer side in the tire radial direction so as not to be damaged. Next, the cut-out bead wire is left on a flat plate, and the inner diameter of the annular body formed by the bead wire in a natural state is measured at eight positions that are evenly spaced on the circumference, and a half of the average value is defined as a curvature radius R.

  According to the present invention, since the bead wire is brazed with a relatively small radius of curvature to reduce the rigidity of the bead wire, the force required for the tire rim assembly is reduced, and therefore the tire rim assembly performance is improved, and consequently the tire It is possible to reduce the amount of RFV in the rim assembly.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tire width direction cross section of a right half portion of a pneumatic tire (hereinafter referred to as “tire”) according to the present invention attached to a standard rim, and FIG. 2 is a cross-sectional perspective view of a bead core of the tire shown in FIG. FIG.

  A tire 1 shown in FIG. 1 is provided with a tread portion 2 that contacts the road surface, a pair of sidewall portions 3 that extend inward in the tire radial direction from both side portions of the tread portion 2, and a tire radial direction of each sidewall portion 3. And a pair of bead portions 5 fitted to the standard rim 4. A toroidal carcass 6 is mounted between the pair of bead parts 5, and an end part thereof is folded from the inner side in the tire width direction toward the outer side in the tire width direction around the bead core 7 embedded in the bead part 5. ing. Further, a belt 8 formed by covering a reinforcing element with rubber is disposed on the outer periphery of the crown portion of the carcass 6.

  As shown in FIG. 2, the bead core 7 has a multilayer structure in which bead wires 9 are laminated in the tire radial direction. The bead wire 9 is continuously brazed with a radius of curvature R in the range of 0.05D to less than 0.45D, preferably 0.2D to 0.4D with respect to the rim diameter D of the standard rim 4 in advance. It has been subjected. Here, the reason why the radius of curvature R is set to 0.05D or more is that it is difficult to process the radius of curvature R to be less than 0.05D, and the rigidity of the bead wire 9 is excessively lowered and the rim assembly property is improved. This is because the resultant pressure becomes too low and the amount of change in RFV after rim assembly increases. On the other hand, when the radius of curvature R is less than 0.45D, if it is 0.45D or more, the rigidity of the bead wire 9 is not sufficiently lowered and the rim assembly property is not sufficiently improved. This is because the amount of change increases.

  And the bead core 7 comprises one bead wire 9 subjected to such brazing, spirally wound continuously in the circumferential direction while shifting the position in the tire width direction to form one layer. It can be formed by forming a plurality of layers in the same procedure as above. Alternatively, a plurality of bead wires 9 subjected to such brazing are arranged in parallel in the tire width direction, and simultaneously wound in the circumferential direction to form one layer, and a plurality of the same procedures are performed on this layer. It can also be formed by forming a layer.

  In general, when a tire rim is assembled, particularly in the case of a rim with a hump, it is necessary to expand the diameter of the bead portion 5 and set the bead seat portion of the rim 4. Since the bead wire 9 constituting it has a low rigidity, the diameter can be increased even with a relatively small force, so that the bead portion can be uniformly fitted (fitted) on the circumference. Further, after the rim assembly, the bead core 7 tries to reduce the diameter by the action of the bead wire 9 having the curvature radius R smaller than the rim diameter D, so that the fitting pressure of the bead portion 5 to the rim 4 is improved.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. .

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

  The tires of Examples 1 to 3 are steel radial tires for passenger cars having a tire size of 205 / 70R15, and have a 4 × 4 strand bead core made of a bead wire having a diameter of 1.3 mm. The bead wires of the tires of these examples are brazed by the curvature radius R shown in Table 1 with respect to the rim diameter D of the standard rim (6J).

  For comparison, a conventional tire having the same configuration as that of Examples 1 to 3 was also produced, except that twice the radius of curvature (2R) of the bead wire brazing R was larger than the rim diameter D. .

  The following items were evaluated for each of the test tires.

(Bead expansion force)
FIG. 3 is a schematic plan view of the apparatus used for evaluating the bead expansion force. The device 10 includes a cylindrical body that is equally divided into eight expansion bodies 11, and each expansion body 11 is configured to be expandable radially outward by an appropriate means. A bead portion B on one side of each test tire is attached to the device 10, and a force F is evenly applied to each expansion body 11 to push the bead portion B apart. A graph was created with the horizontal axis representing the amount of change in diameter when expanded and the vertical axis representing the generated force, the force generated at the rim diameter of the standard bead was read, and the value was evaluated as the bead expansion force. The evaluation results are shown in Table 1.

(Rim fit)
Each of the test tires is attached to a size 6J rim to form a tire wheel, and after applying an internal pressure of 220 kPa (relative pressure) to fit the rim and the tire, a bead portion of the tire wheel is removed using a CT scanner. Observed, the gap between the rim and the bead portion was measured, and the rim fit property was evaluated by the total value of the gaps at 10 locations on the circumference. The evaluation results are shown in Table 1. In addition, the evaluation result of Table 1 is represented by the index | exponent which set the value of the tire of the prior art example to 100, and it is excellent in rim fitting property, so that a numerical value is small.

(Rim slipperiness)
When a load of 4.9 N is applied to the tire wheel placed on the flat plate, the flat plate pressed on the tread portion is slid in this state, and the bead portion slides on the rim. The force applied to the rim was measured, and the rim slip property was evaluated based on the measured value. The evaluation results are shown in Table 1. In addition, the evaluation result of Table 1 is represented by the index | exponent which set the value of the tire of the prior art example to 100, and represents that there are so few rim slips, so that a numerical value is small.

(Air leakage)
The tire wheel was left with the internal pressure applied, the internal pressure after 30 days was measured, and the air leakage was evaluated based on the amount of decrease in the pressure. The evaluation results are shown in Table 1. In addition, the evaluation result of Table 1 is represented with the index | exponent which set the value of the tire of the prior art example to 100, and represents that there are few air leaks, so that a numerical value is small.

  From the results shown in Table 1, in the tires of Examples 1 to 3, the bead expansion force is reduced and the rim assemblability is improved while maintaining the rim slipperiness and the air leakability equal to those of the conventional tire. It can be seen that the rim fit is greatly improved. Therefore, the tires of Examples 1 to 3 are excellent in overall fitting characteristics, and the amount of change in RFV after rim assembly can be minimized.

  As is apparent from the above description, according to the present invention, it is possible to provide a pneumatic tire with improved tire rim assemblability that can suppress the amount of change in RFV after rim assembly to a minimum.

It is a tire width direction sectional view of the right half part of the pneumatic tire according to this invention, and shows the state attached to the standard rim. It is a cross-sectional perspective view of the bead core of the pneumatic tire shown in FIG. It is a schematic plan view of the apparatus used for evaluation of bead expansion force.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Tread part 3 Side wall part 4 Rim 5 Bead part 6 Carcass 7 Bead core 8 Belt 9 Bead wire 10 Bead expansion force evaluation apparatus 11 Expansion body D Rim diameter

Claims (3)

In a bead core for a pneumatic tire formed by annularly winding one or more bead wires,
The bead core is characterized in that the bead core is brazed with a radius of curvature R in a range of 0.05 D or more and less than 0.45 D with respect to a rim diameter D of a standard rim. In a pneumatic tire formed by embedding an annular bead core formed by continuously winding one or more bead wires in a bead portion,
The pneumatic tire is characterized in that the bead wire is brazed with a curvature radius R in a range of 0.05 D or more and less than 0.45 D with respect to a rim diameter D of a standard rim. In the manufacturing method of the pneumatic tire formed by embedding an annular bead core in the bead part,
The bead core is formed by continuously winding one or more bead wires brazed at a radius of curvature R in a range of 0.05D or more and less than 0.45D with respect to a rim diameter D of a standard rim. A method of manufacturing a pneumatic tire.

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