JP4614780B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having a bead structure that achieves both rim detachment resistance and low hump overpressure.

  In a pneumatic tire, if the air pressure decreases for some reason during running, the tire bead may come off the rim. This phenomenon is called rim detachment, and a lateral force is applied to the tire during turning, so that rim detachment is more likely to occur.

In order to prevent rim detachment, the number of bead wires constituting the bead and the total cross-sectional area are increased to increase the strength of the bead and improve rim detachment resistance. In the pneumatic tire disclosed in Patent Document 1, the strength of the bead is increased by providing two bead wires in the cross section of the bead, and the rim removal resistance is improved.
JP-A-3-243404

  However, in the above-described pneumatic tire, when the strength of the bead is increased, the mass of the tire increases, and the tire performance may be deteriorated. In addition, problems such as increased costs and complicated manufacturing processes have occurred.

  On the other hand, when the tire is mounted on the rim, the inner pressure of the tire is gradually increased, and the bead is mounted on the rim by moving the bead along the rim outward in the tire width direction using the expansion of the tire. In order to prevent the rim from coming off, a rim with a hump having a protrusion called a hump on the inner surface of the rim may be used. When a tire is mounted on a rim with a hump, the hump becomes a resistance, so it is necessary to increase the internal pressure to increase the hump overpressure (hump pressure).

  For this reason, when the strength of the bead is increased, a higher internal pressure is required and workability in tire mounting may be lowered, and it is difficult to achieve both rim detachment resistance and low hump overpressure.

  Accordingly, an object of the present invention is to simultaneously realize rim detachment resistance and low hump overpressure.

As a result of intensive studies to solve the above problems, the invention according to claim 1 is directed to a pair of beads, a pair of sidewalls connected to the beads, and a tread connected to the sidewalls to form a toroid shape. In pneumatic tires with rubber,
The bead is disposed on a bead toe side of the first bead wire, a rubber layer adjacent to the bead heel side of the first bead wire, a carcass layer winding the first bead wire and the rubber layer, and the carcass layer. A pneumatic tire comprising a second bead wire and a reinforcing layer around which the carcass layer and the second bead wire are wound is provided.

  When the rim is mounted, the bead gradually moves outward in the tire width direction due to the gradually increased internal pressure and is mounted at a predetermined position. Since the rubber layer is provided on the heel side of the bead that comes into contact with the rim or the rim hump first, the bead heel portion has elasticity. As a result, the tire can be mounted on the rim with a lower hump overpressure.

  By providing the rubber layer, the total cross-sectional area of the first bead wire is reduced, but by providing the second bead wire on the bead toe side, the total cross-sectional areas of the first and second bead wires are secured. As a result, since sufficient strength is obtained as the whole bead, rim removal resistance is ensured.

The invention according to claim 2 is a pneumatic tire comprising a pair of beads, a pair of sidewalls connected to the beads, and a tread rubber connected to the sidewalls to form a toroid shape.
The bead includes a first bead wire, a carcass layer around which the first bead wire is wound, a rubber layer adjacent to a bead heel side of the carcass layer, a second bead wire disposed on a bead toe side of the carcass layer, A pneumatic tire comprising a carcass layer, the rubber layer, and a reinforcing layer around which the second bead wire is wound.

  The invention according to claim 2 is different in that a rubber layer is provided on the bead heel side outside the carcass layer around which the first bead wire is wound, and a second bead wire is provided on the bead toe side. Similarly, the bead heel portion has elasticity due to the rubber layer, and the tire can be attached to the rim with a lower hump overpressure.

  For example, the carcass layer may be made of a commonly used known material (for example, steel), and the reinforcing layer may be made of synthetic fiber such as nylon or rubber.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein a total cross-sectional area of the second bead wire with respect to the first bead wire is 1/5 to 1/8.

  In the pneumatic tire of the present invention, the bead wires are arranged on the heel side and the toe side of the bead. Since the load is imposed by the first bead wire on the bead heel side, it is preferable to increase the total cross-sectional area of the first bead wire. Specifically, the total cross-sectional area of the second bead wire with respect to the first bead wire is preferably 1/5 to 1/8.

  The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein a cross-sectional area of the rubber layer with respect to the first bead wire is 10% to 20%.

  If the cross-sectional area of the rubber layer with respect to the first bead wire exceeds 20%, the strength of the entire bead may be lowered. Conversely, if it is less than 10%, the elasticity on the bead heel side obtained by the rubber layer is insufficient, and a low hump overpressure may not be realized.

  According to the present invention, the rubber layer is provided on the bead heel side to provide elasticity. As a result, the ball side of the bead is deformed when the rim is mounted, and the mounting can be performed with a low hump pressure. In addition, the second bead wire is provided on the bead toe side, and the total cross-sectional area of the first bead wire reduced by the rubber layer is compensated to ensure the bead strength. As a result, rim detachment resistance is improved.

  Hereinafter, embodiments of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a partial cross section including a bead of a pneumatic tire according to the present invention. In the figure, 1 is a bead and 2 is a side wall connected to the bead 1. A tread that is connected to the sidewall 2 to form a toroid shape is not shown.

  The bead 1 will be further described. The first bead wire 3 and the rubber layer 4 are wound by a carcass layer 5. The carcass layer 5 is wound around the first bead wire 3 and the rubber layer 4 from the inner side in the tire width direction, and is folded back and terminated at the outer side in the tire width direction.

  A rubber layer 4 having a lower hardness than the bead filler 10 is disposed so as to cover the bead heel side (tire rotation axis direction outer side) of the first bead wire 3. The rubber layer 4 has a substantially crescent shape in cross section. An area wound around the carcass layer 5 and excluding the rubber layer 4 is filled with a bead filler 10.

  Furthermore, the second bead wire 5 is disposed outside the carcass layer 5 on the bead toe side (inner side in the tire rotation axis direction), and the reinforcing layer 7 covering the carcass layer 5 and the second bead wire 6 is disposed. The reinforcing layer 7 is preferably terminated on the outer side in the tire radial direction than the first bead wire 3.

  Next, the operation of the pneumatic tire according to the present invention will be described. FIG. 2 shows a state where the bead 1 is in contact with the rim R when the rim is mounted. The heel portion 1h of the bead 1 is in contact with the inner end portion of the rim. When the tire air pressure is gradually increased, the bead 1 moves in the direction indicated by the arrow due to the internal pressure. Since the rubber layer 4 is provided on the heel portion 1h side, even if the hump Rh contacts, the bead 1 is deformed by the elasticity of the rubber layer 4 and can easily exceed the hump. As a result, the tire can be attached to the rim with a lower hump overpressure, so that the workability during installation is improved.

  By the way, although the total cross-sectional area of the 1st bead wire 2 has decreased by having arrange | positioned the rubber layer 4, the 2nd bead wire 5 is provided. As a result, the total cross-sectional area of the bead wire is ensured, and the strength of the entire bead is not reduced. Therefore, even if the air pressure decreases and a lateral force is applied, the rim does not come off and the rim detachment resistance is improved.

  As shown in FIG. 3, a rubber layer 4 may be provided on the bead heel side outside the carcass layer 5 around which the first bead wire 3 is wound. In this case, the second bead wire 6 is provided on the bead toe side, and the rubber layer 4, the carcass layer 5, and the second bead wire 6 are wound around the reinforcing layer 7.

  Accordingly, similarly, since the rubber layer 4 is on the heel side, the bead heel portion has elasticity. As a result, the hump pressure can be reduced, and the workability when the rim is mounted is improved.

  Although the hardness of the rubber layer 4 needs to lower the hardness of the bead filler, it is preferable that at least the JIS hardness is 65 degrees or more. If it is less than 65 degrees, the bead strength may decrease.

  The cross-sectional shape of the rubber layer 4 may be other shapes as long as it covers the bead heel side of the first bead wire 3 in addition to the crescent shape. For example, as shown in FIG. 4, the rubber layer 4 may have a cross-sectional shape that covers the bead heel side of the first bead wire 3 with a substantially constant thickness.

  As examples, pneumatic tires according to the present invention and pneumatic tires according to comparative examples and conventional examples were prototyped and performance evaluations were performed. Example 1 has the structure shown in FIG. That is, the first bead wire 3 has a configuration in which two, three, four, five, and four wires (diameter: 1.2 mm) are stacked from the tire rotation axis side. The second bead wire 6 is composed of three wires (diameter 1.2 mm) on the bead toe side. The second embodiment has the same configuration as that of the first embodiment except that the second bead wire 6 is configured by four wires (diameter 1.2 mm).

  Conventional example 1 is a pneumatic tire having a bead structure shown in FIG. 5, and bead wire 11 has a configuration in which 5, 5, 5, 5, and 4 wires (diameter: 1.2 mm) are stacked from the tire rotating shaft side, respectively. is there. Conventional Example 2 has the same configuration as Conventional Example 1 except that bead wire 11 has a configuration in which 5, 5, 5, and 4 wires (diameter: 1.2 mm) are stacked from the tire rotation axis side. The comparative example is a pneumatic tire having the same bead wire configuration as that of the example but not provided with a rubber layer.

  In all cases, the tire size was 195 / 65R15, and performance evaluation was performed by mounting the tire on a standard rim defined by JATMA with a hump.

  The rim detachment pressure is an air pressure when a rim detachment occurs by applying a lateral force to the tire. A tire is installed at a position where the gradient of the movable carriage having a slope plate having a gradient of 10 degrees starts at an angle of 5 degrees from the vertical direction to the opposite side of the slope plate. Then, the movable carriage is pushed with a constant force to apply a lateral force to the tire, and it is checked whether or not the tire has come off the rim. The pressure is reduced by 10 kPa from the air pressure corresponding to the maximum load capacity, and the tire air pressure when the bead is removed is defined as the rim release pressure. The hump overpressure is the air pressure when the bead is completely attached to the rim beyond the hump. In either case, the smaller the number, the better the performance.

  According to Table 1, since the bead wires are provided on the toe side and the heel side of the bead in the comparative example, the rim removal pressure can be lowered, but since the rubber layer is not provided on the heel side, the hump overpressure is increased. Yes. On the other hand, in the tire according to the example, rim detachment resistance and low hump overpressure are realized at the same time.

It is a fragmentary sectional view containing the bead of the pneumatic tire concerning the present invention. It is a figure which shows a mode that a bead moves along a rim. It is a fragmentary sectional view containing the bead of the pneumatic tire concerning the present invention. It is a fragmentary sectional view containing the bead of the pneumatic tire concerning the present invention. It is a fragmentary sectional view containing the bead of the pneumatic tire concerning a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead 2 Side wall 3 1st bead wire 4 Rubber layer 5 Carcass layer 6 2nd bead wire 7 Reinforcing layer

Claims (4)

In a pneumatic tire comprising a pair of beads, a pair of sidewalls connected to the beads, and a tread rubber connected to the sidewalls to form a toroid shape,
The bead is disposed on a bead toe side of the first bead wire, a rubber layer adjacent to the bead heel side of the first bead wire, a carcass layer winding the first bead wire and the rubber layer, and the carcass layer. A pneumatic tire comprising a second bead wire, and a reinforcing layer around which the carcass layer and the second bead wire are wound. In a pneumatic tire comprising a pair of beads, a pair of sidewalls connected to the beads, and a tread rubber connected to the sidewalls to form a toroid shape,
The bead includes a first bead wire, a carcass layer around which the first bead wire is wound, a rubber layer adjacent to a bead heel side of the carcass layer, a second bead wire disposed on a bead toe side of the carcass layer, A pneumatic tire comprising a carcass layer, the rubber layer, and a reinforcing layer around which the second bead wire is wound. The pneumatic tire according to claim 1 or 2, wherein a total cross-sectional area of the second bead wire with respect to the first bead wire is 1/5 to 1/8. The pneumatic tire according to any one of claims 1 to 3, wherein a cross-sectional area of the rubber layer with respect to the first bead wire is 10% to 20%.

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