JP2001055022A - Bead core structure for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bead core structure and a pneumatic tire having the structure capable of obtaining a tire finely keeping a bead wire position at tire manufacturing, having excellent tire durability and steering stability, and improving stiffness distribution fluctuations (uniformity performance) in a tire circumferecial direction. SOLUTION: In a structure of a bead core 1 in a bead portion of a pneumatic tire, bead wires 3 are laminated by winding from the innermost periphery to an outer periphery. A first lamination form T1 wherein the bead wires 3 in an upper layer is laminated generally right above the bead wires 3 in a lower layer, and a second laminating form T2 wherein the bead wires 3 in the upper layer are laminated generally right above a center between the bead wires 3 adjacent to each other in the lower layer are used together. At least the innermost peripheral layer L1 and the second inner peripheral layer L2 are laminated in the second laminated form T2, and the number of lines in the innermost peripheral layer is made to be one line smaller than that of the second inner peripheral layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bead core structure of a bead portion of a pneumatic tire and a pneumatic tire having the bead core structure.

[0002]

2. Description of the Related Art In general, a pneumatic tire includes a pair of annular beads, a sidewall extending from the bead to the outer periphery, and a tread connecting the outer ends of the sidewalls. Is provided. As shown in FIG. 6, a bead core 1 formed as a bundle of bead wires 3 surrounded by a carcass layer 2 is provided in the bead portion B. The bead core 1 has the highest rigidity among the members constituting the tire, and has a bead portion B
Has a role of locking and supporting the end portion of the carcass layer 2 and keeping the bead portion B of the tire fitted on the rim R.

The number and arrangement of the bead wires 3 constituting the above-described bead core 1 vary depending on the tire size and the tire structure. For example, in the case of a tire for a passenger car, 19 tires in a meridional section as shown in FIG. A bead core structure in which bead wires 3 are stacked in a shape close to a rectangle is adopted. In the case of large tires for buses and trucks, a bead core structure having a larger number is adopted.

[0004] Such a bead wire 3 is laminated,
As a method of arranging as shown in FIG. 6, a method of winding a plurality of bead wires 3 arranged in a plurality of rows from the innermost circumference to the outer circumference of the bead core 1 (grommet type) and a method of arranging one bead wire 3 At present, the mainstream is a method (single-strand type) in which a single layer is wound from the innermost circumference to the outer circumference side of the bead core 1 while being wound while sliding in the tire axial direction.

[0005] In the pneumatic tire, an unvulcanized raw material in which a sidewall portion and a tread portion are integrated with a bead portion having a bead core having the above-described structure is placed in a mold having a predetermined shape. It is produced through the steps of pressing and heating and vulcanizing.

[0006]

However, in the above-mentioned conventional bead core structure, in the above-mentioned production process,
Because the tension of the carcass layer is applied to the bead core with a strong force,
The arrangement of the bead wires is easily disturbed, and a tire in which the arrangement is uneven is easily obtained. As a result, the rigidity of the bead core becomes non-uniform, which causes a decrease in the steering stability and the riding comfort characteristics (uniformity performance of the tire). Furthermore, since the shape of the bead core is almost rectangular, stress tends to concentrate on a specific portion of the bead core when the tire is deformed during running, and there is a concern that the durability of the bead portion is reduced.

On the other hand, in recent years, various forms of bead core structures have been proposed from the viewpoints of improving steering stability, ride comfort characteristics, and production efficiency of tires. As one flow of the technique, an upper layer bead wire is laminated almost immediately above the center between adjacent lower layer bead wires, and a unit composed of three bead wires has a lamination form (a so-called “triangular shape”). There is a technique for forming a bead core using only the closest unit (see FIG. 7) (for example, JP-A-7-205618 and JP-A-9-48218). In the bead core structure configured in such a laminated form, the arrangement of each bead wire is less likely to be disturbed in the tire production process, the rigidity of the bead core is uniform, the steering stability of the tire, the durability of the bead portion, etc. Was high.

[0008] However, the bead core structure constituted by the above-mentioned lamination form has a small flexibility in arrangement (displacement) of each bead wire after production of the tire, so that the arrangement on the tire outer peripheral side becomes small, Since the wire filling density is high, the bending and shear stiffness of the bead core are both high, and as a result, there is room for improvement in the flexibility of deformation around the bead with respect to tire deformation. In addition,
Regarding the bead core structure of a tire, there has not been a technique of using two kinds of lamination forms in combination and devising their arrangement.

It is an object of the present invention to provide a bead core which can maintain a good arrangement of bead wires at the time of tire production, has excellent tire durability and ride comfort, and has a further improved steering stability. An object of the present invention is to provide a structure and a pneumatic tire having the structure.

[0010]

The above object can be achieved by the present invention as described below. That is, the bead core structure of the present invention is arranged in a bead portion of a pneumatic tire, and in a bead core structure formed as a bundle of bead wires surrounded by a carcass layer, the bead wire is formed from the innermost periphery of the bead core. When wound around the outer periphery and laminated,
A first lamination form in which an upper bead wire is laminated substantially directly above a lower bead wire, and a second lamination form in which an upper bead wire is laminated substantially immediately above a center between adjacent lower bead wires. And the lamination mode of at least the innermost layer of the bead core and the second layer from the innermost layer is the second lamination mode, and the number of rows of the innermost layer is the innermost layer. The number of rows is one less than the number of rows in the second layer from.

In the above, the laminated form of the outermost layer and the second layer from the outermost layer of the bead core is the second laminated form, and the number of rows of the outermost layer is 2 from the outermost layer.
It is preferable that the number of rows is one less than the number of rows in the second layer.

Further, it is preferable that only the lamination form in the second to fourth layers from the innermost periphery of the bead core is the first lamination form.

On the other hand, the pneumatic tire of the present invention comprises a pair of annular beads, a sidewall extending from the bead to the outer peripheral side, and a tread connecting the outer peripheral ends of the sidewalls. In the pneumatic tire provided, the bead portion has any one of the bead core structures described above.

[Functions and Effects] The present invention has been made based on the results of the following FEM analysis. That is, when the bead wires arranged as shown in FIG. 1 are numbered from 1 to 19, and the stress applied to each bead wire in a state where the tire is mounted is represented by a relative index, FIG. It becomes like the graph shown. According to this, the two wires with the greatest stress correspond to the bead wires (Nos. 1, 3) closest to the bead toe. On the other hand, FIG. 3 shows how much each bead wire arranged around the bead core is displaced in the axial direction and the radial direction of the tire in the tire production process. According to this, the difference between the adjacent bead wires in the amount of displacement in the tire axial direction is the largest between the bead wires Nos. 1 and 2, and the bead wire having the second largest difference in the displacement amount is No. 7 11 bead wires. That is, the arrangement of these bead wires in the tire axial direction is likely to be uneven. In order to investigate the physical properties of a structure, the FEM analysis divides the structure into finite elements, and describes a motion equation (stress is a function of a mass matrix, a damping matrix, a stiffness matrix, and a displacement) described by each element. This is an analysis method for calculating the expression represented by the following formula by calculus or the like, and is used for predicting various characteristics of the tire.

According to the bead core structure of the present invention, at least the innermost layer of the bead core and the second layer from the innermost layer are formed in the second stacked mode, and the number of rows of the innermost layer is reduced. Since the number of rows of the second layer from the innermost circumference is one less than the number of rows, it is a particularly effective improvement measure against the bias of the stress and the displacement of the bead wire predicted from the FEM analysis result. That is, it is possible to prevent the bead wire from being arranged at a portion where the stress is the largest, and to disperse the stress to the two bead wires. Since the bead wires are laminated in the lamination form of No. 2, the reinforcing effect by the adjacent bead wires increases. In addition, since the bead wires are laminated in the second lamination form at a position where unevenness of the arrangement in the tire axial direction is particularly likely to occur between the bead wires, the adjacent bead wires support and reinforce the tire shaft. Nonuniformity in direction can be effectively reduced. As a result, the arrangement of the bead wires is maintained in a good (uniform) state at the time of tire production, so that it is possible to improve the steering stability, ride comfort characteristics, and the like of the tire. In addition, even when the vehicle is running, the second lamination form is adopted in a portion that receives a large tension from the carcass layer when the tire is deformed, so that the tire durability and steering stability can be improved. On the other hand, in a portion where the bias of the stress and the displacement of the bead wire do not cause much problems, the first lamination form is adopted, so that the flexibility of the arrangement (displacement) of each bead wire after tire production becomes large, The arrangement on the side can be made large. For this reason, it deforms flexibly against the shearing force applied to the bead core and increases the reaction force against the bending / torsion force, so that the steering stability of the tire and the rim fit during turning are improved. .

The outermost layer of the bead core and the outermost layer
When the lamination form with the second layer is the second lamination form, and the number of rows of the outermost layer is one less than the number of rows of the second layer from the outermost layer, the following operation is performed. It works. That is, in addition to the above configuration, since the laminated shape of the bead core becomes a more angular shape, by effectively dispersing the stress due to the tension of the carcass layer as described above, the arrangement of the bead wires during tire production. The tire can be maintained well and the durability of the tire can be increased.

The second to fourth from the innermost circumference of the bead core
When only the lamination form of the second layer is the first lamination form, the balance with the second lamination form becomes the most preferable form, and the above-described effects can be more reliably obtained.

On the other hand, since the pneumatic tire of the present invention has the bead core structure described in any of the above, it can exhibit the above-mentioned effects, and can maintain the arrangement of the bead wires during tire production in a good condition. It is possible to provide a pneumatic tire having excellent tire durability and steering stability and further improved rigidity distribution variation (uniformity performance) in the tire circumferential direction.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in the order of a bead core structure and a pneumatic tire with reference to the drawings.

(Bead Core Structure) FIG. 4 (a) shows a meridional section of a bead portion B of a pneumatic tire, and FIG. 4 (b) is an enlarged view of the arrangement of the bead wires in FIG. 4 (a). It is shown. In the present embodiment, from the innermost circumference of the bead core 1, the second lamination form → the first lamination form →
An example is shown in which the bead wires 3 are stacked and arranged in the second stacked mode.

As shown in FIG. 4, a bead core 1 is disposed at a bead portion B of a pneumatic tire, and serves as a bundle of bead wires 3 surrounded by a carcass layer 2 folded from the inside to the outside of the tire. Is formed.

As shown in FIG. 4B, when winding and laminating the bead wire 3 from the innermost periphery to the outer peripheral side of the bead core 1, the upper layer bead wire is disposed almost directly above the lower layer bead wire 3. 3 is used in combination with a second stacking form T2 in which an upper bead wire 3 is stacked almost immediately above the center between adjacent lower bead wires 3. That is, the lamination form between the first layer L1 and the second layer L2 which is the innermost layer is the second lamination form T2, and the lamination form between the second layer L2 and the fourth layer L4 is the first lamination form. The laminated form T1 is a laminated form between the fourth layer L4 and the fifth outermost layer L5 is a second laminated form T2.

The number of columns of the first layer L1, which is the innermost layer, is four, the number of columns of the second layer L2 is five, and the number of columns of the former is one less than the number of columns of the latter. is there. The number of columns of the fifth layer L5, which is the outermost layer, is two, the number of columns of the fourth layer L4 is three, and the number of columns of the former is one less than the number of columns of the latter.

As the material of the bead wire 3, any of various wires conventionally used for tires can be used. For example, a hard steel wire which has been subjected to bronze plating or the like in order to enhance adhesion to rubber. Etc. can be suitably used. The bead wire 3 has a wire diameter of 0.9 to 2.0.
It is preferable to use a 2 mm one.

The gaps between the bead wires 3 are filled with rubber or the like. The bead wires 3 previously coated with the same kind of rubber material as the constituent material of the tire are usually used at the time of lamination. That's why. The interval between the bead wires 3 is substantially determined by the coating thickness of the rubber material or the like, but in consideration of the support / reinforcement effect between the adjacent bead wires 3 in the second laminated form T2.
In the bead wire 3 involved in the second lamination form T2,
It is preferable to reduce the coating thickness. Specifically, the gap of the bead wire 3 at that portion is 0.18 to 0.4.
It is preferable to set it to about 4 mm. On the other hand, as for the bead wire 3 involved in the first lamination form T1, there is no particular limitation on the coating thickness as in the second lamination form T2, but the gap of the bead wire 3 in that part is not more than 0.1 mm.
It is preferable to set it to about 18 to 0.44 mm.

The method of laminating the bead wires 3 may be performed by a single strand type alone or in combination with a grommet type, but it is suitable for the present invention to perform the single strand type only. In other words, a bead wire 3 coated with a rubber raw material is used, and an appropriate jig is used so that the lamination is not easily broken, and the first innermost layer L1 to the fifth outermost layer L5 are used. Until the second lamination form → first
Lamination form → the second lamination form. As a result, a bead core 1 as shown in FIG. 4 is obtained as a laminate.

(Pneumatic Tire) The pneumatic tire of the present invention has a pair of annular beads, a sidewall extending from the bead to the outer peripheral side, and a tread connecting the outer peripheral ends of the sidewalls to each other. And a bead portion having the above-described bead core structure. Therefore, for the portion other than the bead core structure, any of the structure, material, shape, size, and the like of the conventional pneumatic tire can be adopted. Also, the pneumatic tire production process can be performed according to the conventional tire production process, except that the bead core 1 is manufactured using the above-described method of laminating the bead wires 3.

[Another Embodiment] (1) In the above-described embodiment, an example of the bead core structure as shown in FIG. 4 has been described, but the bead core structure as shown in FIGS. 5 (a) to 5 (c) is used. There may be. That is, FIG.
A structure in which the fourth layer L4 of the bead core structure shown in (b) is in five rows and the fifth layer L5 is in four rows (see FIG. 5A), and the first layers L1 and L2 which are the innermost peripheral layers The lamination form between the layers L2 is the second lamination form T2, the lamination form between the second layer L2 and the fifth outermost layer L5 is the first lamination form T1, and the innermost periphery 4 rows, 5 rows, 5 rows from layer to outermost layer
A structure in which rows, five rows, and three rows are stacked (see FIG. 5B), and only a stacked form between the first layer L1 and the second layer L2 as in the bead core structure shown in FIG. 5B Is a second stacked mode T2, and a structure in which the fourth layer L4 has three rows and the fifth layer L5 has two rows (see FIG. 5C) can be employed. That is, the bead core structure of the present invention uses the first laminated form T1 and the second laminated form T2 together, and at least forms the laminated form of the innermost layer of the bead core 1 and the second layer from the innermost layer. Since it is sufficient that the number of rows of the innermost peripheral layer is one row less than the number of rows of the second layer from the innermost circumference, it is sufficient to set the second laminated form T2 and change the laminated form of an arbitrary portion, It is possible to increase or decrease the number of bead wires 3 involved in each lamination form, or to change the arrangement.

The bead core having the bead core structure shown in FIGS. 5A to 5C can be manufactured according to the above-described embodiment.

(2) In the above-described embodiment, a bead core structure composed of a relatively small number of bead wires has been exemplified mainly for tires for passenger cars. In the case of a tire, a bead core structure having a larger number of tires is employed. In any case, it is possible to appropriately reduce the total number or increase the number according to differences in tire size and tire structure.

[0031]

EXAMPLES Examples for confirming the effects of the present invention will be described below. Pneumatic tires (size: 205 / 55R16) each having a bead core structure (bead wire diameter of 1.6 mm) shown in Table 1 were produced, and the following steering stability test, ride comfort test, and water pressure burst test were performed. Was done. Further, the amount of displacement of each bead wire at the time of tire production is calculated by FEM analysis (see FIGS. 3 and 8), and the variation of the amount of displacement is obtained from the distribution, and is calculated as a relative index (the smaller the variation, the smaller the variation). expressed. The number of bead wires in the cross section of the meridian was set to be the same in all examples.

The hydraulic pressure burst test is performed by assembling a test tire into a rim, injecting water into a tube and pressurizing the tube, and determining whether or not a break occurs at a pressure value set based on safety standards. Conventional example 1 is represented by an index with 100 being taken as an index. In the steering stability test, each tire was mounted on a passenger car, and the steering stability was relatively evaluated by a specialized driver from the viewpoint of marginal performance, response performance, straight running performance, etc. displayed. The ride comfort test is
Similarly, the ride comfort is shocked by a professional driver,
It was relatively evaluated from the viewpoint of vibration and the like, and was represented by an index with Conventional Example 1 being 100.

The results are shown in Table 1.

[0034]

[Table 1] As is clear from the above results, in the embodiment of the present invention,
Compared with Conventional Example 1 having only the first lamination form, the variation in the displacement amount was small, and the steering stability, riding comfort and hydraulic burst durability were all improved. Also, the second
The steering stability was improved as compared with Conventional Example 2 consisting of only the laminated form of the above.

[Brief description of the drawings]

FIG. 1 is a view showing the arrangement of bead wires which is a premise of FEM analysis for explaining the operation and effect of the present invention.

FIG. 2 is a graph showing the relationship between the position of a bead wire and stress by FEM analysis for explaining the operation and effect of the present invention.

FIG. 3 is a graph showing the relationship between the position of a bead wire and the amount of displacement by FEM analysis for explaining the operation and effect of the present invention.

FIG. 4 is a meridional sectional view showing an example of a bead core structure of the present invention.

FIG. 5 is a meridian sectional view showing an example of a bead core structure of another embodiment.

FIG. 6 is a meridional sectional view showing an example of a conventional bead core structure.

FIG. 7 is a meridional sectional view showing another example of the conventional bead core structure.

8 is a graph showing the result of calculating the amount of displacement of each bead wire at the time of manufacturing the tire of Example 2 by FEM analysis (corresponding to the conventional example in FIG. 3).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass layer 3 Bead wire B Bead part T1 1st laminated form T2 2nd laminated form L1 Innermost layer (1st layer) L5 Outermost layer

Claims (4)

[Claims] Claims: 1. A pneumatic tire, comprising:
In the structure of a bead core formed as a bundle of bead wires surrounded by a carcass layer, the bead wire is wound from the innermost periphery to the outer peripheral side of the bead core, and is laminated. A first lamination mode in which an upper layer bead wire is laminated directly above and a second lamination mode in which an upper layer bead wire is laminated substantially immediately above a center between adjacent lower layer bead wires; The lamination form of the innermost layer and the second layer from the innermost is the second lamination form, and the number of rows of the innermost layer is smaller than the number of rows of the second layer from the innermost. A bead core structure for a tire, wherein one row is reduced. 2. The laminated form of the outermost layer and the second layer from the outermost layer of the bead core is the second laminated form, and the number of rows of the outermost layer is the number of rows of the second layer from the outermost layer. The bead core structure according to claim 1, wherein the number of rows is one less than the number of rows. 3. The bead core structure according to claim 2, wherein only the lamination form in the second to fourth layers from the innermost periphery of the bead core is the first lamination form. 4. A pneumatic tire comprising: a pair of annular beads; a sidewall extending from the bead to the outer circumference; and a tread connecting the outer circumferences of the sidewalls to each other. A pneumatic tire having a bead core structure according to any one of claims 1 to 3.