JP2018103968A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress lowering of steering stability and generation of air entry in a pneumatic tire having a filler-less structure.SOLUTION: A pneumatic tire of a filler-less structure which comprises a pair of bead portions 1 in which an annular bead core 6 is embedded, and a carcass provided between the pair of bead portions 1, and in which a carcass is folded around without location of a bead filler around the bead core 6. In this tire, the bead core 6 is configured from a body part 61, and an outer peripheral part 62 which is positioned on a tire radial direction outer side of the body part 61. The body part 61 is formed by bead wires 71 which are piled in plural rows in a tire width direction and in plural layers in a tire radial direction with a constant row number, the outer peripheral part 62 is formed by bead wires 72 which are piled in plural rows in the tire width direction and in plural layers on the tire radial direction outer side with a row number being reduced, and a row number in an innermost layer of the outer peripheral part 62 is smaller than a row number in the body part 61.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire having a fillerless structure in which a bead filler is not disposed in a bead portion.

  In general, in a bead portion of a pneumatic tire, a bead core formed of a bead wire and a bead filler formed of hard rubber are embedded, and the carcass is folded around the bead core. On the other hand, a pneumatic tire having a fillerless structure in which a carcass is folded without arranging a bead filler around a bead core is also known, and is disclosed in, for example, Patent Documents 1 to 3. According to the tire having such a structure, since no bead filler is used, the mass and longitudinal rigidity of the tire are reduced, and accordingly the contact area is increased and the shoulder contact pressure is improved, thereby improving rolling resistance and braking performance. An effect is obtained.

  On the other hand, however, the rigidity of the bead portion is weakened, and the bead portion is easily twisted and easily deformed particularly during turning, so that there is a problem that the steering stability performance is lowered. In addition, since the bead filler is omitted, a gap is likely to be formed between the bead core and the carcass folded around the bead core during tire molding, resulting in a process failure called intrusion. It was. Therefore, although a method capable of suppressing the deterioration of the steering stability performance and the occurrence of air entry while maintaining the improvement effect by the filler-less structure is desired, a specific structure suitable for it has not been known.

JP 2012-162204 A JP 2013-39851 A JP2013-63679A

  This invention is made | formed in view of the said situation, The objective is to suppress the fall of steering stability performance and generation | occurrence | production of air entry in the pneumatic tire of a fillerless structure.

  A pneumatic tire according to the present invention includes a pair of bead portions in which an annular bead core is embedded, and a carcass provided between the pair of bead portions, and a bead filler is disposed around the bead core. In a pneumatic tire having a fillerless structure in which the carcass is folded back, the bead core is composed of a main body portion and an outer peripheral portion located on the outer side in the tire radial direction of the main body portion, and the main body portion is a tire. It is formed of bead wires stacked in a plurality of rows in the tire radial direction and in a plurality of rows in the width direction, and the outer peripheral portion is arranged in a plurality of rows in the tire width direction while reducing the number of rows in the tire radial direction. The outermost layer is formed of bead wires stacked in a plurality of layers, and the number of rows in the innermost layer of the outer peripheral portion is smaller than the number of rows in the main body portion.

  In this tire, since the outer peripheral portion formed by stacking the bead wires is disposed on the outer side in the tire radial direction of the main body portion of the bead core, it is possible to increase the rigidity of the bead portion and suppress the deterioration of the steering stability performance. The outer peripheral portion is formed of bead wires stacked in a plurality of layers outward in the tire radial direction while reducing the number of rows in a plurality of rows in the tire width direction, and has a tapered shape as a whole. Therefore, the gap between the bead core and the carcass can be reduced, and the occurrence of air can be suppressed. Further, since the number of rows in the innermost layer of the outer peripheral portion is smaller than the number of rows in the main body portion, the size of the outer peripheral portion is appropriately reduced, which is convenient for maintaining the improvement effect by the fillerless structure.

  It is preferable that the difference between the number of rows of the main body portion and the number of rows of the innermost layer of the outer peripheral portion is 2 or more. According to such a configuration, the size of the outer peripheral portion is more reliably reduced, which is more convenient for maintaining the improvement effect by the fillerless structure such as reduction of rolling resistance and improvement of braking performance.

  It is preferable that the number of rows of the outermost layer of the outer peripheral portion is 1. According to such a configuration, since the outermost layer of the outer peripheral portion is formed thin, it is possible to appropriately reduce the gap between the bead core and the carcass and satisfactorily suppress the occurrence of air entry.

  (Claim 4) is preferred. According to such a configuration, it is possible to appropriately reduce the gap between the bead core and the carcass and satisfactorily suppress the occurrence of air entry.

  It is preferable that the width center position of the outer peripheral portion is disposed on the outer side in the tire width direction than the width center position of the main body portion. In this case, since the outer peripheral portion is moved outward in the tire width direction, the rigidity of the bead portion on the outer side in the tire width direction is increased. During turning of the vehicle, a portion on the outer side in the tire width direction in the bead portion is particularly greatly twisted and deformed. Therefore, according to such a configuration, it is possible to effectively suppress a decrease in steering stability performance.

  What the said outer peripheral part is distribute | arranged to the position which does not protrude in a tire width direction rather than the said main-body part is preferable. Thereby, generation | occurrence | production of air can be suppressed favorably so that an unnecessary clearance gap may not be formed between a bead core and a carcass.

  It is preferable that the number of rows of the main body is 5 or more and the number of layers is 4 or more. A bead core having such a main body is useful as a bead core provided in a tire of a size that can be expected to have a large improvement effect due to the fillerless structure.

The tire meridian half sectional view schematically showing an example of the pneumatic tire according to the present invention Enlarged view of the bead core shown in FIG. Schematic diagram showing a modification of the bead core Schematic diagram showing a modification of the bead core Schematic diagram showing a modification of the bead core Schematic diagram showing bead cores of Comparative Examples 1 and 2 Schematic showing the bead core of Comparative Example 3

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

  The pneumatic tire T shown in FIG. 1 includes a pair of bead portions 1 in which an annular bead core 6 is embedded, and a carcass 4 provided between the pair of bead portions 1. Further, the tire T is embedded in the tread portion 3, a sidewall portion 2 extending outward in the tire radial direction from each of the bead portions 1, a tread portion 3 connected to each tire radial direction outer end of the sidewall portion 2, and the tread portion 3. Belt 5.

  The carcass 4 is formed by a ply (carcass ply) formed by rubber coating a plurality of cords arranged in a direction substantially orthogonal to the tire circumferential direction. The cord material is preferably a metal such as steel or an organic fiber such as polyester, rayon, nylon, or aramid. In the present embodiment, since the carcass 4 is composed of a single ply, it is lighter than a case where a plurality of plies are stacked. This is advantageous in enhancing the effectiveness of a fillerless structure that is intended to reduce rolling resistance.

  The carcass 4 reaches the bead portion 1 from the tread portion 3 through the sidewall portion 2, and an end portion thereof is folded around the bead core 6 from the inner side to the outer side in the tire width direction. In other words, the carcass 4 is provided with a series of folded plies arranged on the outer side in the tire width direction of the bead core 6 on the main body ply from the tread portion 3 through the sidewall portion 2 to the bead portion 1. The height H4 of the folded end of the carcass 4 with respect to the rim base line is preferably 0.4 to 0.5 times the tire cross-section height TH. Thereby, the distribution of the tension acting on the carcass 4 at the time of tire molding is stabilized, leading to a reduction in the defect rate.

  The belt 5 is formed by a ply (belt ply) in which a cord extending incline with respect to the tire circumferential direction is covered with rubber. The belt 5 is composed of a plurality of (two in the present embodiment) plies, and the cords are laminated so that the cords cross each other in opposite directions. On the outer periphery of the belt 5, a belt reinforcing material formed by rubber-covering a cord extending substantially in the tire circumferential direction may be provided. By disposing the belt reinforcing material so as to cover both ends of the belt 5, it is possible to suppress the lifting of the belt 5 due to the centrifugal force during high-speed running and improve the high-speed durability.

  The tire T is a pneumatic tire having a filler-less structure in which the carcass 4 is folded without disposing a bead filler around the bead core 6. In a general pneumatic tire, a bead filler made of hard rubber is embedded in the bead portion 1, but in this pneumatic tire T, such a bead filler is omitted, and the body ply and the folded ply Only the bead core 6 is disposed therebetween. According to such a fillerless structure, the tire mass and longitudinal rigidity are reduced, and the accompanying increase in the contact area and improvement in the shoulder contact pressure can provide an improvement effect such as reduction in rolling resistance and improvement in braking performance.

  FIG. 2 is an enlarged view of the bead core 6 shown in FIG. In FIG. 2, the right side is the outer side in the tire width direction, and the left side is the inner side in the tire width direction. The bead core 6 is formed by stacking the bead wires 7 in a plurality of rows in the tire width direction and in a plurality of layers in the tire radial direction. The bead wire 7 may be a multifilament cord obtained by twisting a plurality of filaments, or may be a monofilament cord constituted by a single filament. The material of the bead wire 7 is not particularly limited, but a steel wire is preferably used.

  The bead core 6 includes a main body portion 61 and an outer peripheral portion 62 located on the outer side of the main body portion 61 in the tire radial direction. The cross-sectional shape of the main body 61 is rectangular like a broken line BL1 surrounding it, and the cross-sectional shape of the outer peripheral part 62 is triangular like a broken line BL2 surrounding it. Therefore, the bead core 6 has a cross-sectional shape as if a triangle was placed on a rectangle as a whole. For convenience of explanation, the bead wires 7 forming the main body portion 61 and the outer peripheral portion 62 are denoted by different symbols, bead wires 71 and 72, respectively, but they may be the same bead wire.

  The main body 61 is formed of bead wires 71 stacked in a plurality of rows in the tire width direction and in a plurality of layers in the tire radial direction with a fixed number of rows. In the present embodiment, the bead wires 71 are stacked in four layers in the tire radial direction in five rows in the tire width direction and at a constant number of rows (that is, constant in five rows). That is, the main body 61 has a 5-row 4-layer structure. The main body 61 may be either a single strand type or a grommet type. In the former, one rubber-coated bead wire is wound in a spiral shape. In the latter, a converging body formed by covering a plurality of bead wires arranged in parallel with rubber is wound in a spiral shape.

  The outer peripheral portion 62 is formed by bead wires 72 stacked in a plurality of layers outward in the tire radial direction while reducing the number of rows in a plurality of rows in the tire width direction. In this embodiment, the bead wires 72 are stacked in two layers outward in the tire radial direction while reducing the number of rows in two rows in the tire width direction. That is, the outer peripheral portion 62 has a two-row two-layer structure. The outer peripheral portion 62 may be either a single strand type or a grommet type, but is preferably the former. In that case, the bead wire 72 may be continuous from the bead wire 71 forming the main body 61 or may be discontinuous.

  Since the number of rows of the outer peripheral portion 62 is two or more and the number of layers is two or more, at least three bead wires 72 appear in the cross section of the bead portion 1. As shown in FIG. 2, the number of rows in the innermost layer of the outer peripheral portion 62 is smaller than the number of rows in the main body portion 61. In this embodiment, since the number of rows of the main body portion 61 is 5, the number of rows of the innermost layer of the outer peripheral portion 62 is in the range of 2 to 4, and the number of rows of the innermost layer of the outer peripheral portion 62 in this example is two. is there. The innermost layer of the outer peripheral portion 62 refers to the innermost layer in the tire radial direction in the outer peripheral portion 62, and the outermost layer of the outer peripheral portion 62 described later refers to the outermost layer in the tire radial direction in the outer peripheral portion 62.

  In this bead core 6, since the outer peripheral portion 62 as described above is disposed on the outer side in the tire radial direction of the main body portion 61, the rigidity of the bead portion 1 can be increased and the deterioration of the steering stability performance can be suppressed. The outer peripheral portion 62 is formed of bead wires 72 stacked in a plurality of layers in a plurality of rows in the tire width direction and in the tire radial direction while reducing the number of rows, and has a tapered shape as a whole. Therefore, the bead core 6 and the carcass 4 The generation of air can be suppressed by reducing the gap between the two. Moreover, since the number of rows of the innermost layer of the outer peripheral portion 62 is smaller than the number of rows of the main body portion 61, the size of the outer peripheral portion 62 is appropriately reduced, which is convenient for maintaining the improvement effect by the fillerless structure.

  In order to compensate for the rigidity reduction of the bead portion 1 due to the adoption of the fillerless structure, a method of providing a reinforcing layer including a cord such as an organic fiber on the outside of the carcass is known, and disclosed in, for example, Patent Document 2 listed above. Yes. However, in the present embodiment, in view of the original purpose of the fillerless structure to reduce the longitudinal rigidity of the tire, such a reinforcing layer is not provided, and the folded portion (folded ply) of the carcass 4 is A rubber member constituting the outer surface of the bead portion 1 is directly bonded.

  It is preferable that the number of rows of the main body portion 61 is 5 or more and the number of layers is 4 or more. The bead core 6 having such a main body 61 is useful as a bead core provided in a tire of a size that can be expected to greatly improve the fillerless structure. A tire having a size that can greatly improve the effect of the fillerless structure is, for example, a tire having a rim diameter of 16 inches or more. The rim diameter of the tire T is displayed on the surface of the sidewall portion 2 as a tire size.

  The outer peripheral portion 62 is formed by bead wires 72 stacked in a plurality of layers outward in the tire radial direction while reducing the number of rows one by one in the tire width direction. As a result, the rigidity of the bead core 6 gradually decreases along the tire radial direction, and a sudden change in rigidity is avoided. In addition, the number of rows of the outermost layer of the outer peripheral portion 62 is 1, and according to this, since the outermost layer of the outer peripheral portion 62 is formed thin, the gap between the bead core 6 and the carcass 4 is appropriately reduced, The occurrence of air can be suppressed satisfactorily. In view of the original purpose of the fillerless structure to reduce the longitudinal rigidity of the tire, the number of layers of the outer peripheral portion 62 is preferably equal to or less than the number of layers of the main body portion 61.

  In the present embodiment, the broken line BL2 surrounding the outer peripheral portion 62 forms an equilateral triangle, and the bead wires 72 forming the outer peripheral portion 62 are stacked in an equilateral triangle shape. According to such a configuration, generation of air can be satisfactorily suppressed by preventing an unnecessary gap from being formed between the bead core 6 and the carcass 4. In this case, the bead wires 72 are arranged in a staggered manner in the cross section of the outer peripheral portion 62. On the other hand, a structure in which the bead wires 72 forming the outer peripheral portion 62 are stacked in a right triangle shape is also conceivable (see FIG. 5), but from the viewpoint of suppressing air entry, the structure in which the bead wires 72 are stacked in this way is considered. Is preferred.

  3 to 5 show modified examples of the bead core 6, respectively. Since these components have the same configuration as that of the above-described embodiment except for those described below, common points will be omitted and differences will be mainly described. The same parts as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  3A shows an example in which the outer peripheral portion 62 has a three-row three-layer structure, and FIG. 3B shows an example in which the outer peripheral portion 62 has a four-row four-layer structure. The difference between the number of rows of the main body portion 61 and the number of rows of the innermost layer of the outer peripheral portion 62 is 3 in FIG. 2 and 2 in FIG. As described above, the difference between the number of rows of the main body portion 61 and the number of rows of the innermost layer of the outer peripheral portion 62 is preferably 2 or more. According to such a configuration, the size of the outer peripheral portion 62 is more reliably reduced, which is convenient for maintaining the improvement effect by the fillerless structure such as reduction of rolling resistance and improvement of braking performance.

  FIG. 4 shows an example in which the width center position 62 c of the outer peripheral portion 62 is arranged on the outer side in the tire width direction than the width center position 61 c of the main body portion 61. The width center positions 61c and 62c indicate the center positions in the tire width direction in the main body portion 61 and the outer peripheral portion 62, respectively. In the present embodiment, the width center position 62c is disposed on the outer side in the tire width direction by 20% of the bead core width from the width center position 61c. In this case, since the outer peripheral part 62 is brought closer to the outer side in the tire width direction, the rigidity of the outer part in the tire width direction of the bead part 1 is enhanced as compared with the embodiment of FIG. During turning of the vehicle, a portion on the outer side in the tire width direction in the bead portion 1 is particularly greatly twisted and deformed. Therefore, according to such a configuration, it is possible to effectively suppress a decrease in steering stability performance.

  FIG. 5 shows an example in which the bead wires 72 forming the outer peripheral portion 62 are stacked in a right triangle shape. A broken line BL2 surrounding the outer peripheral portion 62 forms a right triangle. In this example, similarly to the embodiment of FIG. 4, the width center position 62 c of the outer peripheral portion 62 is arranged on the outer side in the tire width direction than the width center position 61 c of the main body portion 61. In this configuration, since the outer peripheral portion 62 is fully moved toward the outer side in the tire width direction, it is possible to more effectively suppress a decrease in steering stability performance.

  From the viewpoint of suppressing the occurrence of air entering between the bead core 6 and the carcass 4, the outer peripheral portion 62 is preferably arranged at a position that does not protrude in the tire width direction from the main body portion 61. Therefore, when the outer peripheral portion 62 is disposed close to the outer side in the tire width direction as shown in FIGS. 4 and 5, it is desirable not to project the outer peripheral portion 62 from the main body portion 61 outward in the tire width direction.

  The pneumatic tire of the present invention can be configured in the same manner as a conventionally known fillerless structure pneumatic tire except that the bead core is configured as described above, and includes conventionally known materials, shapes, structures, manufacturing methods, and the like. Either can be employed in the present invention.

  Examples that specifically illustrate the structure and effects of the present invention will be described.

(1) Rolling resistance
The rolling resistance was measured according to the test method specified in JIS D 4234 (ISO28580), and the measured value was calculated. The tire used for the evaluation was mounted on a standard rim, and the air pressure was 250 kPa. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the smaller the numerical value, the smaller the rolling resistance and the better.

(2) Braking performance The braking distance from when the vehicle running at 100 km / h to full braking by the operation of the ABS to stopping was measured, and the reciprocal of the measured value was calculated. The tires used for evaluation were mounted on standard rims and filled with vehicle-designated air pressure. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the larger the value, the better the braking performance.

(3) Steering stability The tire is run on a belt using a flat belt cornering tester, and the difference in cornering force when the side slip angle is changed by ± 1 degree is calculated as the angle difference (2 degrees). The value obtained by dividing the value was used as an indicator of steering stability performance. The tire used for the evaluation was mounted on a standard rim, and the air pressure was 250 kPa. The traveling conditions were a speed of 10 km / h and a load of 4.83 kN. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the larger the value, the better the steering stability performance.

(4) Air entering defect rate The ratio of the number of air entering defects between the bead core and the carcass to the number of products produced was obtained, and the reciprocal thereof was calculated. The result of Comparative Example 1 is evaluated as an index with a value of 100, and the smaller the numerical value, the smaller the occurrence of air entry defects and the better.

Comparative Examples and Examples Comparative Examples 1 to 3 and Examples 1 and 2 were made by changing the form of the bead core in the tire of size 205 / 60R16 92V. Comparative Example 1 has a general structure having a bead filler as shown by a broken line in FIG. On the other hand, Comparative Examples 2 and 3 and Examples 1 and 2 both have a filler-less structure that does not include a bead filler. Other tire configurations are common to the examples. The evaluation results are shown in Table 1.

  As shown in Table 1, with respect to rolling resistance and braking performance, Examples 1 and 2 are superior to Comparative Example 1 that does not have a fillerless structure, and are comparable to Comparative Examples 2 and 3 that have a fillerless structure. . Nevertheless, with respect to steering stability performance and air entry, the results of Examples 1 and 2 are as good as or better than those of Comparative Examples 2 and 3.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Carcass 5 Belt 6 Bead core 7 Bead wire 61 Main body part 62 Outer peripheral part 71 Bead wire 72 Bead wire T Pneumatic tire

Claims (7)

A fillerless comprising a pair of bead portions in which an annular bead core is embedded and a carcass provided between the pair of bead portions, wherein the carcass is folded without disposing a bead filler around the bead core. In the pneumatic tire of structure,
The bead core is composed of a main body part and an outer peripheral part located on the outer side in the tire radial direction of the main body part,
The main body is formed of bead wires stacked in a plurality of layers in the tire radial direction in a plurality of rows in the tire width direction and in a fixed number of rows,
The outer peripheral portion is formed of bead wires stacked in a plurality of layers outward in the tire radial direction while reducing the number of rows in a plurality of rows in the tire width direction, and the number of rows of the innermost layer of the outer peripheral portion is the number of the main body portion Pneumatic tire characterized by fewer than the number of rows.   The pneumatic tire according to claim 1, wherein a difference between the number of rows of the main body portion and the number of rows of the innermost layer of the outer peripheral portion is 2 or more.   The pneumatic tire according to claim 1 or 2, wherein the number of rows of the outermost layer of the outer peripheral portion is one.   The pneumatic tire according to any one of claims 1 to 3, wherein the bead wires forming the outer peripheral portion are stacked in an equilateral triangle shape.   The pneumatic tire according to any one of claims 1 to 4, wherein a width center position of the outer peripheral portion is arranged on an outer side in a tire width direction than a width center position of the main body portion.   The pneumatic tire according to any one of claims 1 to 5, wherein the outer peripheral portion is arranged at a position that does not protrude in the tire width direction from the main body portion.   The pneumatic tire according to claim 1, wherein the number of rows of the main body portions is 5 or more and the number of layers is 4 or more.

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