JP5891025B2 - Bead core and pneumatic tire - Google Patents

Description

  The present invention relates to a bead core for a tire and a pneumatic tire using the bead core, and particularly relates to a bead core formed using a thin plate metal material and a pneumatic tire using the bead core.

  In general, a bead core is embedded in a bead portion of a pneumatic tire from the viewpoint of improving the fit between a tire and a rim. The bead core embedded in the bead portion also functions as a locking member that locks the carcass extending in a toroid shape from the tread portion to the pair of bead portions via the pair of sidewall portions.

Here, conventionally, as the bead core, an annular body formed by winding a steel wire having a circular cross section covered with rubber is used.
However, a bead core formed by winding a steel wire having a circular cross section after being covered with rubber is not sufficient in rotational rigidity as a whole bead core. For example, as shown in FIG. When the pulling force F toward is applied, there is a problem that the entire bead core 6A is greatly deformed. That is, in a tire using a bead core 6A formed by winding a rubber-coated steel wire 61A, the entire bead core 6A is greatly rotated and deformed at the time of internal pressure filling or the like. Failure may occur due to pulling out of the carcass 4 that has been stopped or the occurrence of stress (tensile stress) at the end (turned end) of the carcass 4.

  Therefore, in Patent Document 1, for example, a bead core is formed by winding bead wires having a square cross section so as to contact each other in both the tire width direction and the tire radial direction, thereby increasing the contact area between adjacent bead wires. It has been proposed to increase the rotational rigidity of the entire bead core.

JP-A 49-119301

  However, in the conventional bead core formed by winding a bead wire having a square cross section, the bead wires are brought into contact with both the tire width direction and the tire radial direction by winding a plurality of bead wires arranged in parallel in the tire width direction. Therefore, when an external force f is applied to the bead core, the positions of the bead wires 61B are displaced in the bead core 6B as shown in FIG. 6, and the shape of the bead core 6B may be broken. That is, in the tire using the conventional bead core, when the shape of the bead core collapses as shown in FIG. 6, the rotational rigidity of the bead core as a whole decreases, and as a result, the durability of the bead portion decreases. There was a problem that.

  In recent years, from the viewpoint of improving fuel efficiency and reducing environmental impact, tire weight reduction has been demanded, and it is possible to reduce the weight of a member while ensuring performance such as strength even for a bead core. It has been demanded.

  Therefore, an object of the present invention is to provide a bead core capable of reducing weight while ensuring sufficient rotational rigidity and strength. Another object of the present invention is to provide a lightweight pneumatic tire having a bead portion with high durability by using the bead core.

  The present inventors have intensively studied to achieve the above object. Then, the inventors have formed a bead core using a thin plate-shaped metal material having a predetermined aspect ratio in cross-sectional shape, so that the shape is not easily collapsed even when an external force is applied, and sufficient The present invention has been completed by finding that a bead core capable of reducing the weight while ensuring a sufficient rotational rigidity and strength can be provided.

That is, this invention aims to solve the above-mentioned problem advantageously, and the bead core of the present invention is a bead core for a tire, and is an annular body formed using a metal plate-like body. The annular body has a laminated structure formed by laminating the plate-like bodies so that the plate-like bodies directly overlap each other in the thickness direction of the plate-like bodies . An aspect ratio (long side / short side) is 10 to 60, and the cross section in the width direction is rectangular. In this way, if a laminated structure in which metal plate-like bodies are laminated in the thickness direction of the plate-like body is adopted, sufficient rotation rigidity can be obtained as a whole bead core, and the shape retention of the bead core against external force can be achieved. Can be increased. In addition, if the bead core is formed using a plate-like body having an aspect ratio of 10 to 60 in the cross section in the width direction, the weight of the bead core can be reduced while ensuring sufficient strength. Incidentally, the bead core of the present invention preferably has an aspect ratio (long side / short side) of 10 to 50.
In the present invention, “to laminate a plate-like body in the thickness direction of the plate-like body” includes not only a case where a plurality of plate-like bodies are stacked to form a laminated structure, but also a single plate-like body. The case where a laminated structure is formed by winding is also included.

  Here, in the bead core of the present invention, it is preferable that the annular body is formed by winding the plate-like body. This is because a bead core can be easily manufactured by winding a plate-like body to form an annular body.

  Moreover, it is preferable that the bead core of this invention has the said laminated structure that the number of lamination | stacking is 4-30. This is because if the number of laminated layers is 4 or more, the strength of the bead core can be sufficiently secured. Further, if the number of laminated layers is 30 or less, the bead core can be sufficiently reduced in weight.

Further, in the bead core of the present invention, it is preferable that a cross section in the width direction of the plate-like body has a long side length of 5 to 30 mm and a short side length of 0.5 to 2.0 mm. If a plate-like body having a long side length of 5 to 30 mm and a short side length of 0.5 to 2.0 mm is used, the strength of the plate-like body is secured and the bead core This is because the weight can be further reduced. Moreover, it is because the uniformity (uniformity) of the circumferential direction of a bead core can be improved if the plate-shaped body whose length of a short side is 0.5-2.0 mm is used.
In the present invention, “long side” refers to the maximum length in the longitudinal direction of the cross section in the width direction of the plate-like body (that is, the maximum width of the plate-like body), and “short side” refers to the plate-like body. The maximum length in the direction perpendicular to the longitudinal direction of the cross section in the width direction (that is, the maximum thickness of the plate-like body) is indicated.

And as for the bead core of this invention, it is preferable that the said plate-shaped object consists of a rolled steel plate. This is because the steel sheet rolled so that the aspect ratio of the cross section in the width direction is 10 or more has a sufficiently high strength (particularly, breaking strength).

  Moreover, this invention aims at solving the said subject advantageously, The pneumatic tire of this invention uses any of the said bead cores, It is characterized by the above-mentioned. Thus, if the bead core mentioned above is used, the durability of a bead part is high and can provide a lightweight pneumatic tire.

  ADVANTAGE OF THE INVENTION According to this invention, the bead core which can reduce a weight can be provided, ensuring sufficient rotational rigidity and intensity | strength. Moreover, according to this invention, the durability of a bead part is high and can provide a lightweight pneumatic tire.

1 is a tire width direction cross-sectional view of a typical pneumatic tire according to the present invention. It is a figure which expands and shows the tire width direction cross section of the bead part of the pneumatic tire shown in FIG. 1 is a side view of an exemplary bead core according to the present invention. FIG. It is a figure which shows the cross section which follows the II line | wire of the bead core shown in FIG. It is a figure explaining the rotational deformation of the bead core at the time of internal pressure filling about the pneumatic tire which has the conventional bead core formed by winding the steel wire of circular section. It is a figure explaining collapse of the shape of a bead core when external force is loaded to a bead core about a pneumatic tire which has a conventional bead core formed by winding a bead wire with a square cross section.

  Embodiments of the present invention will be described below with reference to the drawings. The pneumatic tire of the present invention is characterized by using the bead core of the present invention. And the bead core of this invention was formed using the metal plate-shaped body which cross-sectional shape has a predetermined aspect-ratio (long side / short side).

<Pneumatic tire>
Here, FIG. 1 shows a cross section in the tire width direction in an unloaded state in which an example of a pneumatic tire according to the present invention is mounted on an applicable rim R and a predetermined internal pressure (maximum air pressure) prescribed in JATMA or the like is applied.

A pneumatic tire 10 shown in FIG. 1 is connected to a tread portion 1, a pair of sidewall portions 2 that extend inward in the tire radial direction from the side portions of the tread portion 1, and a tire radial direction inward of each sidewall portion 2. And a bead portion 3.
Further, the pneumatic tire 10 includes a radial carcass 4 made of one ply extending between the pair of bead portions 3. Here, the radial carcass 4 extends in a toroidal shape from the tread portion 1 to the pair of bead portions 3 via the pair of sidewall portions 2, and the tire width around the bead core 6 having a square cross section embedded in the bead portion 3. It is folded from the inner side in the direction toward the outer side in the tire width direction. A bead filler 7 is disposed outside the bead core 6 in the tire radial direction of the bead portion 3.
Further, a belt 5 composed of two layers of belt layers 51 and 52 is installed on the outer side in the tire radial direction (outer crown side) of the radial carcass 4 of the tread portion 1. A tread rubber 8 is disposed on the outer side in the tire radial direction of the belt 5, and a plurality (three in FIG. 1) extending in the tire circumferential direction are provided on the surface layer portion (tread portion tread side) of the tread rubber 8. ) Main grooves 9 are formed so as to be line symmetric about the tire equator C.

The pneumatic tire 10 shown in FIG. 1 is characterized in that an annular bead core 6 described in detail below is embedded in the bead portion 3.
In addition, as shown in an enlarged view of the cross section of the bead portion 3 in FIG. 2, the bead core 6 having a square cross section is not particularly limited and is inclined at a predetermined angle θ ₁ with respect to the tire width direction. Incidentally, the angle θ ₁ can be set such that the bead seat of the application rim R and the inner peripheral surface of the bead core 6 are substantially parallel (for example, 15 ° or less).

<Bead core>
Here, FIG. 3 shows a schematic side view of an example of a bead core according to the present invention. The bead core 6 shown in FIG. 3 is formed of an annular body formed using a metal plate-like body 61, and is used as a bead core for a pneumatic tire. The bead core 6 is characterized in that a plate-like body having a predetermined aspect ratio in the cross section in the width direction is used as the plate-like body 61.

More specifically, the bead core 6 is formed by winding a plate-like body 61 having a constant width so that a side view is shown in FIG. 3 and a cross section taken along line II in FIG. 3 is shown in FIG. It consists of an annular body. In the bead core 6 shown in FIG. 3, the plate-like body 61 is wound without being covered with rubber or the like (that is, without interposing rubber). Then, the winding start end 62 and the winding end end 63 of the plate-like body 61 are located at different circumferential positions. The virtual plane passing through the central axis of the bead core 6 and the winding start end 62 and the virtual plane passing through the central axis of the bead core 6 and the winding end 63 intersect at an angle θ ₂ (for example, 60 to 90 °). doing.

  Further, as shown in FIG. 4, the bead core 6 has a laminated structure in which a cross section in the width direction is formed by laminating plate-like bodies 61 in one direction (vertical direction in FIG. 4). That is, as shown in FIG. 4, the bead core 6 made of an annular body formed by winding a single plate-like body 61 is wound so that the plate-like bodies 61 directly overlap in the stacking direction. The cross section taken along the line II of the bead core 6 has a shape in which rectangles corresponding to the cross section in the width direction of the plate-like body 61 are stacked in one direction (the thickness direction of the plate-like body 61).

  And the cross section in the width direction of the plate-like body 61 constituting the bead core 6 has a rectangular shape, and the aspect ratio (long side length / short side length) of the cross section in the width direction is 3 to 60. It is within the range. That is, in a cross-sectional view along the central axis of the annular bead core 6, the long side length a (corresponding to the width of the plate-like body) of the cross-section of the plate-like body 61 constituting each layer of the laminated structure and the short side length The ratio (a / b) to b (corresponding to the thickness of the plate-like body) is in the range of 3 to 60. The aspect ratio (a / b) is preferably 10-50.

Here, the formation of the above-described bead core 6 (annular body) is not particularly limited, and can be performed by winding the plate-like body 61 around the outer periphery of the drum. Incidentally, when the bead core 6 is inclined at a predetermined angle θ ₁ with respect to the tire width direction and embedded in the bead portion 3 as shown in FIG. The bead core 6 can be formed by wrapping around the outer periphery of the bead core 6.

And according to the said bead core 6, the weight of the bead core 6 can be reduced, ensuring sufficient rotational rigidity and intensity | strength.
That is, since the bead core 6 has a laminated structure in which metal plate-like bodies 61 are laminated, a contact area between the plate-like bodies 61 that directly overlap in the lamination direction (thickness direction of the plate-like body 61) is large. Thus, the catching effect between the plate-like bodies 61 is increased. Therefore, the bead core 6 has sufficiently high rotational rigidity as the whole bead core 6 when embedded in the bead portion 3.
Moreover, since the bead core 6 has a laminated structure in which metal plate-like bodies 61 are laminated, an external force is applied as compared with a conventional bead core in which a plurality of wires are arranged in parallel in the tire width direction and wound. Even if it is a case, the shape is difficult to collapse. More specifically, the shape of the bead core 6 does not collapse even when an external force is applied in the stacking direction, and even when the external force is applied in a direction perpendicular to the stacking direction, Since the aspect ratio (a / b) of the body 61 is large, the shape does not collapse greatly.
Further, since the bead core 6 uses the plate-like body 61 having an aspect ratio (a / b) of 3 or more in cross-sectional shape, the unit volume is compared with the case where a thick plate-like body having an aspect ratio of less than 3 is used. The breaking strength of the hit plate-like body 61 can be increased sufficiently to ensure sufficient strength. Moreover, since the plate-like body 61 having an aspect ratio (a / b) of 60 or less is used, the thickness of the plate-like body 61 is suppressed from being uneven, and the strength of the bead core 6 is prevented from being lowered. can do.
Since the bead core 6 has sufficient rotational rigidity and strength as described above, even if the number of turns of the plate-like body 61 is reduced and the thickness and weight of the bead core 6 are reduced, sufficient rotation is achieved. Rigidity and strength can be ensured.

  Therefore, in the pneumatic tire 10 using the bead core 6, it is possible to achieve both the rotational rigidity and strength of the bead core 6 and the weight reduction of the bead core 6, thereby suppressing a decrease in durability of the bead portion 3. However, the tire weight can be reduced.

  Here, the plate-like body 61 is preferably made of a rolled steel plate such as a cold rolled steel plate or a hot rolled steel plate. This is because the steel sheet has a sufficiently high strength (particularly, breaking strength) when it is thinly rolled so that the aspect ratio of the cross section in the width direction is 3 or more, particularly 10 or more.

Moreover, as for the cross section of the plate-shaped body 61 in the width direction, it is preferable that the long side length a is 5 to 30 mm, and the short side length b is 0.5 to 2.0 mm. If the plate-like body 61 having a short side length of 2.0 mm or less and a long side length of 5 mm or more is used, the breaking strength of the plate-like body is further increased, and the strength of the bead core 6 is increased. This is because it can be secured sufficiently. In addition, the plate-like body 61 having a short side length of less than 0.5 mm and the plate-like body 61 having a long side length of more than 30 mm are difficult to manufacture with a uniform thickness. Furthermore, if the length of the short side is 2.0 mm or less, when the plate-like body 61 is wound and laminated, an overlap portion (other part) is located between the winding start end 62 and the winding end end 63. This is because it is possible to reduce the difference in thickness between the portion other than the overlap portion and the circumferential uniformity of the bead core from being reduced. . That is, if the length a of the long side and the length b of the short side are within the above ranges, the bead core 6 can be reduced in weight while ensuring sufficient strength, and the bead core 6 and the bead core 6 are used. This is because the circumferential uniformity of the pneumatic tire can be improved.
In addition, from the viewpoint of securing the uniformity in the circumferential direction of the bead core 6 while suppressing the concentration of stress due to the winding start end 62 and the winding end end 63 being positioned close to each other in the circumferential direction, the angle θ ₂ is It is preferable that it is 60-90 degrees.

  Furthermore, the number of stacked layers, that is, the number of windings of the plate-like body 61 is preferably 4 to 30. This is because if the number of laminated layers is 4 or more, the strength of the bead core can be sufficiently secured. Further, if the number of laminated layers is 30 or less, the bead core can be sufficiently reduced in weight.

  As mentioned above, although embodiment of this invention was described with reference to drawings, the bead core and pneumatic tire of this invention are not limited to the example mentioned above, A change is suitably carried out to the bead core and pneumatic tire of this invention. Can be added.

  Specifically, the bead core 6 of the above example is formed by winding a single plate-like body 61, but the bead core of the present invention is formed by winding and laminating a plurality of plate-like bodies one by one. May be. The bead core of the present invention may be formed by laminating an annular plate (in the width direction of the bead core). However, from the viewpoint of easily manufacturing a bead core, it is preferable to form a bead core by winding a single plate-like body.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

( Reference Example 1 )
Using the rolled steel plate, a bead core having the configuration shown in FIGS. Next, using the produced bead core, a pneumatic tire having a size of 275 / 80R22.5 having a cross-sectional shape as shown in FIG. 1 was manufactured according to a conventional method.
And about the produced tire, the tire weight, the uniformity, and durability of the bead part were evaluated by the following method. The results are shown in Table 1.

(Examples 2 to 5, Comparative Example 1)
A bead core and a pneumatic tire were produced in the same manner as in Reference Example 1 except that the specifications of the bead core were changed as shown in Table 1.
And about the produced tire, the tire weight, the uniformity, and durability of the bead part were evaluated by the same method as in Reference Example 1 . The results are shown in Table 1.

(Conventional example 1)
With the specifications shown in Table 1, a bead core having the configuration shown in FIG. 5 was produced. As the steel wire, a wire having a diameter of 1.83 mm was used. Next, using the produced bead core, a pneumatic tire having a size of 275 / 80R22.5 having a cross-sectional shape as shown in FIG. 1 was manufactured according to a conventional method.
And about the produced tire, the tire weight, the uniformity, and durability of the bead part were evaluated by the same method as in Reference Example 1 . The results are shown in Table 1.

<Tire weight>
The mass of the produced tire was measured. The index was evaluated with the mass of Conventional Example 1 as 100. In the table, the smaller the value, the lighter.
<Uniformity>
Mount the prepared tire on the applicable rim, fill the inside with air so that the internal pressure becomes 900 kPa (relative pressure), and then use a drum testing machine having a hub with a load cell (tire mounting portion to the drum). The drum running test was conducted under the condition of applying a normal load. And the fluctuation | variation of the up-down, left-right, and front-back force during one rotation of a tire was measured, and index evaluation was performed by setting the uniformity of the prior art example 1 to 100. In the table, the larger the value, the higher the uniformity.
<Durability of bead part>
The prepared tire was mounted on an applied rim, and after the inside was filled with air so that the internal pressure became 900 kPa (relative pressure), the running distance until the bead portion failed was measured using a drum testing machine. The measurement conditions were room temperature: 45 ° C., load: 180% of normal load (57 kN), and speed: 60 km / h. Then, index evaluation was performed with the travel distance of Conventional Example 1 being 100. In the table, the larger the numerical value, the longer the travel distance until the bead part breaks down and the higher the bead part durability (that is, the higher the rotational rigidity and strength).

From Table 1, it can be seen that the tires of Examples 3 to 5 are excellent in bead portion durability and lightweight. Moreover, since the tire of Example 2 is very excellent in bead part durability, it turns out that weight can be reduced (that is, there exists room for weight reduction), ensuring sufficient rotational rigidity and intensity | strength. . Furthermore, it turns out that the pneumatic tire using the bead core of Examples 2-5 is excellent in uniformity.

  ADVANTAGE OF THE INVENTION According to this invention, the bead core which can reduce a weight can be provided, ensuring sufficient rotational rigidity and intensity | strength. Moreover, according to this invention, the durability of a bead part is high and can provide a lightweight pneumatic tire.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Radial carcass 5 Belt 6 Bead core 6A Bead core 6B Bead core 7 Bead filler 8 Tread rubber 9 Main groove 10 Pneumatic tire 51, 52 Belt layer 61 Plate body (rolled steel plate)
61A Steel wire 61B Bead wire 62 Winding start end 63 Winding end R Applicable rim

Claims (7)

A bead core for a tire,
It consists of an annular body formed using a metal plate,
The annular body has a laminated structure in which the plate-like bodies are laminated so that the plate-like bodies directly overlap each other in the thickness direction of the plate-like bodies ,
The cross-section in the width direction of the plate-like body has an aspect ratio (long side / short side) of 10 to 60,
The bead core is characterized in that the cross section in the width direction is rectangular.   The bead core according to claim 1, wherein the annular body is formed by winding the plate-like body.   The bead core according to claim 1, wherein the laminated structure has 4 to 30 laminated layers.   The bead core according to any one of claims 1 to 3, wherein the aspect ratio (long side / short side) is 10 to 50.   5. The cross-section in the width direction of the plate-like body has a long side length of 5 to 30 mm and a short side length of 0.5 to 2.0 mm. Crab bead core.   The bead core according to any one of claims 1 to 5, wherein the plate-like body is made of a rolled steel plate.   A pneumatic tire using the bead core according to claim 1.

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