JP2012224129A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which realizes the reduction of weight without deteriorating steering stability.SOLUTION: The pneumatic tire 1 comprise a pair of bead cores 2, a ply body part 3 locked to the bead cores 2 and extending in a toroidal shape, a carcass 5 formed of a ply folding back part 4 extending from both ends of the ply body part 3 and folded back around each of the bead cores 2 and a bead filler 6 extending in a tapered form toward a tire radial direction D from a position adjacent to each of the bead cores 2 between the ply body part 3 and ply folding back part 4. When an imaginary straight line m orthogonal to the carcass line is drawn a from the outermost position P situated in the outermost part in the tire radial direction in which an outer surface 1a of the pneumatic tire 1 comes into contact with a rim flange Rf of a normal rim R in a cross section in the tire width direction, the bead filler 6 has a constricted part 14 having a rubber thickness t1 made locally thin on each of the bead cores 2 side from the imaginary straight line m.

Description

  The present invention relates to a pneumatic tire that is reduced in weight without deteriorating steering stability.

  In recent years, due to demands for improving the fuel efficiency of vehicles, it has become necessary to reduce the weight of tires in tires mounted on vehicles.

  As a conventional means for reducing the tire weight, for example, as described in Patent Document 1, the bead filler rubber is reduced in size or the rubber thickness is reduced to reduce the rubber volume of the bead filler. Reduction.

  However, it is not preferable to simply reduce the rubber volume of the bead filler because the steering stability is deteriorated as a result of a reduction in tire side rigidity.

  Moreover, in patent document 1, in order to compensate for the steering stability deteriorated by downsizing the bead apex rubber, the side wall rubber includes an inner rubber layer that optimizes a complex elastic modulus in the tire circumferential direction, and an outer rubber. In this configuration, the rigidity of the bead part itself, which is the tire part mounted on the rim, remains low, so that the tire during load rolling is sufficient. It does not work well, and as a result, satisfactory handling stability cannot be obtained, and in addition, the side wall rubber is composed of two rubber layers. In addition, there is a problem that the number of work steps increases because an additional bonding step is required.

JP 2007-45361 A

  The object of the present invention is to optimize the cross-sectional shape of the bead filler and effectively reduce the rubber volume of the bead filler, thereby reducing the weight without deteriorating the steering stability. Is to provide.

In order to achieve the above object, the gist of the present invention is as follows.
(1) a pair of bead cores, a ply body portion that is locked to the bead core and extends in a toroid shape, and a carcass that includes ply folding portions that extend from both ends of the ply body portion and are folded around each of the bead cores. A pneumatic tire having a bead filler extending in a tapered shape from a position adjacent to the bead core between the ply main body portion and the ply turn-up portion, and the pneumatic tire is attached to a regular rim. In the cross section of the tire in the width direction of the no-load state with normal internal pressure, the outer surface of the tire and the rim flange of the normal rim are in contact with each other, orthogonal to the carcass line from the outermost position on the outermost side in the tire radial direction. When drawing a virtual straight line, the bead filler has a locally thinner rubber thickness on the bead core side than the virtual straight line. A pneumatic tire characterized by having a fin portion.

(2) The rubber thickness of the constricted portion is t1, the maximum rubber thickness of the bead filler portion between the constricted portion and the outer end position in the tire radial direction of the bead filler is t2, and the bead filler is adjacent to the bead core. The pneumatic tire according to (1), wherein the rubber thicknesses t1, t2, and t3 satisfy the relationship of 0.5 ≦ t1 / t2 ≦ 0.95 and 0.3 ≦ t2 / t3 ≦ 1.0 when the rubber thickness of the portion is t3.

(3) The outer diameter position of the bead filler in the tire radial direction is more outward in the tire radial direction than the virtual straight line, and the distance measured in the direction orthogonal to the virtual straight line is 10 mm or more (1) or ( 2) The pneumatic tire as described.

  According to the present invention, a pneumatic tire capable of reducing the weight without deteriorating steering stability by optimizing the cross-sectional shape of the bead filler and effectively reducing the rubber volume of the bead filler. It became possible to provide.

1 is a half-sectional view in the width direction of a pneumatic tire according to the present invention. (A) is the width direction half sectional view of the pneumatic tire of the comparative example 1, (b) is the width direction half sectional view of the pneumatic tire of the comparative example 2.

Next, embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a half-section in the width direction of a pneumatic tire according to the present invention.
A pneumatic tire 1 shown in FIG. 1 includes a pair of bead cores 2 (only one side is shown), a ply main body 3 that is locked to the bead core 2 and extends in a toroid shape, and extends from both ends of the ply main body 3. 2 between the carcass 5 formed of the ply turn-up portion 4 folded around each of the two, the ply main body portion 3 and the ply turn-up portion 4 from the position adjacent to the bead core 2 to the outside in the tire radial direction D. And a bead filler 6 extending in a tapered shape. In FIG. 1, the carcass 5 is configured with one ply. However, the carcass 5 may be configured with a plurality of plies. In the case of a plurality of plies, the carcass 5 may be not only a radial ply but also a bias ply.

  Further, in the pneumatic tire 1 shown in FIG. 1, as an example, two cord rubber coating layers 7 a and 7 b are disposed on the outer periphery of the crown portion 5 a of the carcass 5 so that the cords intersect with the tire equator E. A belt 8 formed by lamination, a narrow protective layer (layer layer) 9 (only one side is shown) which is located at both ends of the belt 8 and is formed of a pair of cord rubber coating layers, and an outer side in the tire radial direction of the belt 8 Although it is shown in FIG. 2 and is composed of a two-layer structure of a base rubber 10 and a cap rubber 11 and further includes a tread rubber 13 provided with a tread groove 12, the belt is not limited to this configuration. It can be composed of one or more cord rubber coating layers, or can be provided with a wide protective layer (cap layer) consisting of a wide cord rubber coating layer covering the entire outer surface of the belt, , Tre Dogomu can also be a single layer structure or a stacked structure of three or more layers, the tread grooves also depending on the application, the number may change extending direction, the cross-sectional shape and the like as appropriate.

  The main configuration of the present invention is to optimize the cross-sectional shape of the bead filler 6 and to effectively reduce the rubber volume of the bead filler 6. The outermost surface 1a of the tire 1 and the rim flange Rf of the regular rim R are in contact with each other in the tire radial direction cross section in the tire width direction section that is attached to the regular rim R, has a regular internal pressure, and is in a no-load state. When an imaginary straight line m orthogonal to the carcass line of the carcass main body 3 is drawn from the outer position P, the bead filler 6 has a constricted portion where the rubber thickness t1 is locally thinner on the bead core 2 side than the imaginary straight line m. By adopting this configuration, it is possible to effectively reduce the weight without deteriorating the steering stability. In addition, the rim assembly property is improved by reducing the rubber volume of the bead filler.

  The “regular rim” here means “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The “regular internal pressure” is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO.

  The reason why the constricted portion 14 of the bead filler 6 is provided on the bead core 2 side with respect to the imaginary straight line m is that the constricted portion 14, which is a portion obtained by reducing the volume of the bead filler 6, is imaginary. This is because the constricted portion 14 is supported by the rim flange even if it is provided on the bead core side with respect to the straight line m, so that the influence on the side rigidity is not so much. In the case where the constricted portion 14 is provided on the tread side, the support by the rim flange cannot be received, and therefore, the deformation amount of the tire side portion at the time of tire load rolling increases, and the steering stability deteriorates. .

  Therefore, in the present invention, the constricted portion 14 of the bead filler 6 is provided on the bead core 2 side with respect to the imaginary straight line m.

  Further, the rubber thickness of the constricted portion 14 is t1, the maximum rubber thickness of the bead filler portion between the constricted portion 14 and the tire radial direction outer end position 15 of the bead filler 6 is t2, and the bead core 2 of the bead filler 6 is used. It is preferable that the rubber thicknesses t1, t2, and t3 satisfy the relationship of 0.5 ≦ t1 / t2 ≦ 0.95 and 0.3 ≦ t2 / t3 ≦ 1.0, where t3 is the thickness of the rubber adjacent to the portion.

  If t1 / t2 is less than 0.5, the rubber thickness t1 of the constricted portion 14 of the bead filler 6 becomes too thin, so that even if there is a rim flange support, the side rigidity tends to decrease and the steering stability tends to deteriorate. This is because if the t1 / t2 exceeds 0.95, the effect of reducing the tire weight is not significant.

  Further, if t2 / t3 is less than 0.3, the side rigidity is insufficient and the steering stability may be deteriorated. If t2 / t3 exceeds 1.0, the effect of reducing the tire weight is not significant. This is because the side rigidity becomes too high and the ride comfort is deteriorated, which is not preferable.

  Furthermore, it is preferable that the outer end position 15 in the tire radial direction of the bead filler 6 is more outward in the tire radial direction than the virtual straight line m and the distance measured in the direction orthogonal to the virtual straight line m is 10 mm or more. This is because when the distance is less than 10 mm, the side rigidity is insufficient and the steering stability may be deteriorated.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

Next, a pneumatic tire according to the present invention was prototyped and its performance was evaluated, which will be described below.
The tire of the example is a pneumatic tire for passenger cars having the tire structure shown in FIG. 1 and having a tire size of 195 / 65R15, and was produced according to the specifications shown in Table 1. For comparison, a comparative example 1 and a comparative example 2 having a tire structure similar to the tire of the example except that the tire size is 195 / 65R15 and the bead filler is not provided with a constricted portion were also prototyped. The tire structure of the tire of Comparative Example 1 is shown in FIG. 2 (a), and the tire structure of the tire of Comparative Example 2 is shown in FIG. 2 (b). And performance evaluation was performed about the tire weight and steering stability. Steering stability was evaluated by feeling evaluation by a professional driver on the test course. Table 1 shows the evaluation results. The rubber volume, tire weight, and steering stability values of the bead filler shown in Table 1 are all indicated by an index ratio when Comparative Example 1 is set to 100, and the bead filler rubber volume and tire weight. The smaller the numerical value, the smaller the rubber volume and the tire weight, and the larger the steering stability value, the better.

  From the evaluation results shown in Table 1, it can be seen that, in comparison with Comparative Example 1, the example has the same handling stability and the tire weight is reduced. Here, since the proportional relationship is generally established between the rubber volume of the bead filler and the weight of the bead filler, the embodiment has a particularly large weight of the bead filler as compared with the first comparative example while maintaining steering stability. It can be seen that it can be reduced. On the other hand, although the rubber volume of the bead filler was the same as that of the example, the comparative example 2 in which the constricted portion was not provided was significantly inferior in handling stability to the example and the comparative example 1.

  According to the present invention, a pneumatic tire capable of reducing the weight without deteriorating steering stability by optimizing the cross-sectional shape of the bead filler and effectively reducing the rubber volume of the bead filler. It became possible to provide.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead core 3 Ply main-body part 4 Ply folding | turning part 5 Carcass 6 Bead filler 7a, 7b Cord rubber coating layer 8 Belt 9 Narrow width protective layer (layer layer)
DESCRIPTION OF SYMBOLS 10 Base rubber 11 Cap rubber 12 Tread groove 13 Tread rubber 14 Neck part 15 Tire radial direction outer end position of bead filler 6 20, 30 Pneumatic tire

Claims (3)

A pair of bead cores,
A carcass constituted by a ply main body portion that is locked to the bead core and extends in a toroid shape, and a ply folded portion that extends from both ends of the ply main body portion and is folded around each of the bead cores;
In a pneumatic tire comprising a bead filler extending in a tapered shape from a position adjacent to a bead core between the ply body part and the ply folded part in a tire radial direction,
When the pneumatic tire is mounted on a regular rim and has a regular internal pressure, the outer surface of the tire and the rim flange of the regular rim are in contact with each other in the tire width direction cross section in a no-load state. When drawing a virtual straight line perpendicular to the carcass line from the outside position,
The pneumatic tire according to claim 1, wherein the bead filler has a constricted portion in which a rubber thickness is locally reduced on a bead core side with respect to the virtual straight line. The rubber thickness of the constricted portion is t1, the maximum rubber thickness of the bead filler portion between the constricted portion and the outer end position in the tire radial direction of the bead filler is t2, and the rubber of the bead filler adjacent to the bead core When the thickness is t3, each rubber thickness t1, t2, t3 is
0.5 ≦ t1 / t2 ≦ 0.95
0.3 ≦ t2 / t3 ≦ 1.0
The pneumatic tire according to claim 1, wherein the relationship is satisfied.   3. The pneumatic tire according to claim 1, wherein the outer end position of the bead filler in the tire radial direction is more outward than the virtual straight line in the tire radial direction, and a distance measured in a direction orthogonal to the virtual straight line is 10 mm or more. tire.

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