JP3198063B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a tire apex having a multilayer structure in which two or more rubber materials are laminated in an annual ring shape or a spiral shape to provide a lateral rigidity, a bead durability and a riding property of a tire. The present invention relates to a pneumatic tire that can greatly improve comfort and balance comfort.

[0002]

2. Description of the Related Art A bead portion of a tire is provided with a bead apex which rises radially outward from a bead core in order to increase lateral rigidity and obtain necessary steering stability.

[0003] The bead apex has a problem of a trade-off that the steering stability is improved by increasing its rubber volume, rubber hardness and the like, but conversely impairs ride comfort. For the purpose of improvement, see, for example, Japanese Patent Application Laid-Open No. 3-248903.
As shown in FIG. 9A, a bead apex A is formed of a lower layer B made of a hard rubber on a bead core side.
1 and an upper layer B2 made of a soft rubber adjacent to the outer side in the radial direction.
As shown in FIG. 9 (B), the bead apex A includes a core rubber C1 on the bead core side made of hard rubber containing organic short fibers, and a sheath for covering the core rubber C1 except for the bottom surface. Techniques for forming with rubber C2 have been proposed.

[0004]

However, FIG.
The former shown in (A) can improve the steering stability and the riding comfort to some extent as compared with the case where the bead apex is formed of only one kind of rubber material. The drawback of poor ride comfort still remains, and no satisfactory improvement has been achieved.
In addition, the upper side of the bead apex is made of only soft rubber, so that it tends to be soft and lacks in lateral rigidity, and it is easy to cause the tire to be stiff when turning. The lower layer B1 and the upper layer B
A large stress due to the difference in hardness acts on the boundary surface Bs with the surface 2 to easily cause interfacial peeling, and in the case of a tire, strain concentrates on this portion, and bead damage such as looseness tends to occur.

On the other hand, in the case of the latter shown in FIG. 9 (B), the boundary area between the core rubber C1 and the sheath rubber C2 is increased, so that the interface peeling is reduced, but the hard core rubber C1 exists only at the center. Therefore, similarly to the former, it is difficult to sufficiently increase the lateral rigidity without impairing the riding comfort.

Accordingly, the present invention provides a bead apex,
Based on the fact that two or more types of rubber materials having different hardnesses are formed in a multilayer structure laminated in an annual ring shape or a spiral shape, the effect of improving the lateral rigidity, bead durability and ride comfort of the tire can be further enhanced. It aims to provide pneumatic tires.

[0007]

In order to achieve the above object, the invention according to claim 1 of the present invention comprises a main body portion extending from a tread portion to a sidewall portion to a bead core of a bead portion. A carcass having a folded portion connected to the body portion and folded around the bead core; and a carcass interposed between the body portion and the folded portion of the carcass, extending outward from the bead core in a tire radial direction and having a different rubber hardness. And a bead apex made of two or more types of rubber materials, and the bead apex has a rubber ring made of each of the rubber materials extending from the center of the bead apex to an outer peripheral surface of the bead apex in a meridional section of the tire, and has a ring-shaped or spiral shape. And a rubber layer extending from the center of the bead apex to the outer peripheral surface of the bead apex. That was available, characterized in that it was the number of layers of 3 or more.

In order to ensure the effects of the present invention, among the rubber materials forming the bead apex, the hardest rubber material has a JISA hardness Hh and the softest rubber material has a JI hardness Hh.
The difference Hh-Hs from the SA hardness Hs is preferably set to 2 degrees or more.

Further, such a multilayered bead apex can be easily formed by extruding a plurality of rubber materials at a time by using a screw shaft type extruder. Preferably, the number of layers is 7 or more.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In the figure, a pneumatic tire 1
Has a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both sides thereof, and a bead portion 4 located at the radially inner end of each sidewall portion 3 in the present example. The tire is formed as a flat radial tire for passenger cars with the nominal flattening rate set to 0.80 or less, for example, about 0.60.

The tire 1 has a carcass 6 extending between the bead portions 4, a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2, and a bead core 5 of the bead portion 4. And a bead apex 8 extending radially outward from the front end.

The belt layer 7 is composed of a plurality of belt plies 7A and 7B, in this example, inner and outer belt plies. The cords are arranged at an angle of ３０30 ° and are arranged in different directions so that the cords cross each other between the plies 7A and 7B. The belt layer 7 is required to have high rigidity in order to obtain the required high-speed running performance,
As the belt cord, a substantially inextensible cord such as an aromatic polyamide fiber cord and a steel cord, particularly a steel cord, is preferably used. Also, as a tire for a passenger car, a crossed arrangement of cords composed of two belt plies is preferably used as in this example from the viewpoint of rigidity / weight.

In the present embodiment, a band layer 10 is provided on the outer side of the belt layer 7 to cover at least an outer end portion of the belt layer 7 in the tire axial direction, thereby suppressing lifting of the belt layer 7 during high-speed running. Are illustrated.

In the present embodiment, the band layer 10 includes a full band 10A that covers the entire outer surface of the belt layer 7, and a small band that is interposed between the full band 10A and the belt layer 7 and covers only the outer end portion of the belt. Each of the bands 10A and 10B has a width and a pair of edge bands 10B, and is formed by, for example, spirally winding the band cord at an angle of 0 to 5 degrees with respect to the tire equator C. As the band cord, an organic fiber cord having a tensile modulus of less than 1000 kg / mm ² and having a low elasticity such as nylon, rayon or polyester, particularly a nylon fiber cord excellent in bending resistance and workability is preferably used. .

The carcass 6 includes a toroidal main body 11 extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the side wall portion 3, and a tire shaft connected to the main body portion 11 and around the bead core 5. And a folded portion 12 folded from the inside to the outside in the direction. The carcass 6 is formed from at least one carcass ply 6A, 6B in which carcass cords are arranged at an angle of, for example, 70 to 90 degrees with respect to the tire equator C. In such tires, organic fiber cords such as nylon, polyester, and rayon are preferably used as carcass cords.

The bead apex 8 is made of two or more types of rubber materials having different rubber hardnesses, in this example, two types of a hard rubber material H and a soft rubber material S. Bead core 5 passing between the
Is formed in a substantially triangular cross section which extends in a tapered shape from the upper surface of the tire in the radial direction of the tire.

The bead apex 8 is formed as a multilayer structure 16 in which a rubber layer composed of the rubber materials H and S extends from the center of the bead apex to the outer peripheral surface of the bead apex and is laminated in a ring shape or spiral shape on the meridional section of the tire. Is done.

In this example, a case of an annual ring-shaped multilayer structure 16A is shown, and a bead apex 8 is formed by a core-shaped rubber layer 2 disposed at the center P thereof as schematically shown in FIG.
1A and a multilayer structure 16 including six annular rubber layers 21B to 22F, which are sequentially stacked around the rubber layer 1A, and each rubber layer has a different rubber hardness between adjacent rubber layers. Are classified. FIG. 3 shows a case where the rubber layers 21A, 21C and 21E are formed of a hard rubber material H and the rubber layers 21B, 21D and 21F are formed of a soft rubber material S, for example. It is good also as composition.

Here, when the rubber layers 21B to 21F are formed in a ring shape, the rubber layers 21B to 21F forming the annular shape are formed by the core-shaped rubber layers 2B.
It is necessary to go around the 1A without interruption.

In such a multilayer structure 16A, since the rubber layers 21C and 21E made of hard rubber H are arranged at a distance from the bending center i, high bending rigidity is exhibited. For example, as shown in FIG. 8A which models the structure of the bead apex A in FIG. 9B, a soft rubber piece 14A having a thickness T2 is provided on both sides of a central hard rubber piece 13A having a thickness T1. 8B, a soft rubber piece 14B having a thickness of 2 × T2 as shown in FIG. 8B, and a hard rubber piece 13B having a thickness of 0.5 × T1 on both sides. Since the hard rubber piece 13B is arranged at a distance from the bending center i, it can be understood that the bending rigidity becomes larger. Moreover, in the multilayer structure 16A of this example, the hard rubber layers 21C and 21E can exhibit higher bending stiffness because the second moment of area has a large annular shape.

On the other hand, the impact force applied to the bead apex 8 is widely propagated over the entire apex by forming a multilayer structure, thereby causing distortion between the entire layers due to a difference in rubber hardness. As a result, the impact energy received from the road surface is largely absorbed, and excellent impact absorption, that is, riding comfort is exhibited.

Moreover, the stress acting on the interface between the rubber layers is
As described above, since it is widely dispersed at the interface of the entire annual ring, the stress applied to a certain area is small, and peeling damage is suppressed, and durability is improved. In addition, since a laminate is also formed near the outer end of the bead apex 8, the rigidity gradually increases inward in the radial direction from the vicinity of the outer end, so that the phenomenon that the tire is not stiff is reliably prevented and the vicinity of the outer end is also improved. Can also increase the durability.

The effects of improving the bending stiffness, shock absorption, and durability increase as the number of layers increases, and therefore the number of layers is preferably 5 or more, more preferably 10 or more.

The bead apex 8 forming the multilayer structure 16 has a contour shape of a bead apex of a conventional tire,
Although it can be used according to the size, etc., in order to reflect and exert the above-mentioned improvement effect on steering stability, ride comfort, and bead durability in tire performance, it is necessary to use a bead base at the outer end of the bead apex 8. The height TB in the radial direction from the line is 0.15 of the tire section height TC.
It is preferable to increase it by a factor of two or more.

The height BT of the apex itself, which is the height in the radial direction from the upper surface of the bead core 5 to the outer end of the bead apex 8, is determined by the maximum thickness BW of the bead apex 8.
If it exceeds 10 times, the vicinity of the outer end of the bead apex 8 is likely to be deformed during tire molding, impairing moldability and reducing tire uniformity. It is easy to be.

Also, of the above rubber materials, the difference Hh-Hs between the JISA hardness Hh of the hardest rubber material and the JISA hardness Hs of the softest rubber material, that is, in this example, the JISA hardness Hh of the rubber material H The difference Hh-Hs from the JISA hardness Hs of the rubber material S is preferably set to 2 degrees or more, and if it is less than 2 degrees, the above-mentioned improvement effect is not sufficiently exhibited. Therefore, it is more preferable that the difference be 4 degrees or more. On the other hand, in order to increase this difference while securing a constant tire lateral rigidity, it is necessary to increase the hardness Hh. When the hardness Hh is excessive, cracks are likely to occur. Therefore, the difference is preferably set to 10 degrees or less.

The hardness Hh, Hs is 50-100.
The degree of hardness can be selected according to the required tire performance within the range of degrees, but in order to secure sufficient tire lateral rigidity, the hardness Hh is in the range of 90 to 98 degrees, and the hardness Hs is 87 degrees.
It is preferable to set it in the range of -93 degrees.

Further, when the weight ratio between the rubber materials is uneven, one of the rubber layers is too thin to easily become a discontinuous annual ring shape, and it is difficult to obtain a uniform and reliable multilayer structure.
Further, there is a possibility that the effects of the present application cannot be sufficiently achieved. Therefore, when two types of rubber materials H and S are used as in this example,
The weight Wh, Ws of each rubber material is preferably in the range of 10 to 90%, more preferably in the range of 30 to 70% of the total weight Wh + Ws of the bead apec.

As shown in FIG. 3, the annual ring-shaped multilayer structure 16A has a rubber layer 21B, 21C,... The multilayer body 18 can be formed by forming the wound multilayer body 18 and then subjecting the multilayer body to a forming process into a predetermined sectional shape.

Next, FIG. 4 shows a case where the bead apex 8 is a spirally laminated multilayer structure 16B. In the figure, the multilayer structure 16B is formed by continuously and spirally winding a rubber layer 22 made of a rubber material H and a rubber layer 23 made of a rubber material S adjacent to each other. The number of rubber layers laminated from the center of the apex to the outer peripheral surface of the bead apex may vary depending on the measurement position. That is, in this example, the number of laminations from the center P to the bottom surface 8a is 5, the number of laminations to the right slope 8b is 6, and the number of laminations to the left slope 8c is 7. Therefore, in the case of the spiral multilayer structure 16B, the minimum number of layers is defined as the number of layers of the bead apex 8, and
Set this number to 3 or more.

In the spiral multi-layer structure 16B, since the number of laminations is three or more and the rubber material exhibits high viscosity, the spiral multi-layer structure 16B exhibits almost the same function as the annual ring-shaped multi-layer structure 16A. Excellent improvement effects in rigidity, shock absorption, and durability can be achieved.

Also in the case of the multilayer structure 16B, the number of laminations, the JISA hardness Hh and Hs of the rubber material, the hardness difference Hh-Hs of the rubber material, the weight ratio of each rubber material, the height TB of the upper end of the bead apex, Regarding the preferable setting range in the height BT of the apex itself, the preferable setting range in the annual ring-shaped multilayer structure 16A can be applied for the same reason.

The spiral multi-layer structure 16B is formed by continuously winding the sheet-like rubber layers 22 and 23 made of rubber materials H and S in a spiral shape while overlapping them, thereby forming a wound body in advance. Thereafter, the wound multilayer body 18 is added to the wound body.
Similarly to the above, it can be formed by performing a molding process to a predetermined sectional shape. In the bead apex 8 formed by such a method, as shown in FIG. 5 showing a cross section in the longitudinal direction, each rubber layer is arranged substantially in parallel in the longitudinal direction.

The multilayer structure 16 can also be formed by using an extruder 31 having a screw shaft 30, as shown in FIG. More specifically, the screw shaft 3
0, for example, rubber materials H, S
The rubber material between the fins 33 and 33 is pushed toward the extrusion port while being twisted in the direction of arrow 34 by gradually feeding the two layers of rubber material in which Thus, the multilayer structure 16 is formed. At this time, as the screw shaft 30 is longer, that is, as the number of pitches of the fins 33 is larger, the number of laminations can be increased, which is preferable. The time is too long, which results in rubber burning and the like. Therefore, the extruder 31
When is used, the number of layers is preferably 40 or less, more preferably 30 or less. Conversely, when the number of laminations is less than 7, rubber kneading becomes insufficient and the shape of the extruded product becomes unstable, and rubber extruded easily at the edge of the extruded product.
Therefore, the number of layers is preferably 7 or more, and more preferably 10 or more.

In the bead apex 8 using the extruder 31, the rubber layers are laminated while exhibiting a substantially conical shape in the longitudinal direction, as shown in FIG. 7 showing a cross section in the longitudinal direction. Thereby, the shock absorption and durability can be further improved.

Further, three, four or more rubber materials can be used as the rubber material, and the order of lamination can be freely set when such a variety of types are used.

The pneumatic tire of the present invention may employ a bias structure in addition to the radial structure, and may be formed as tires for various structural purposes such as tires for passenger cars, tires for heavy loads, and tires for motorcycles. it can.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG. 1 and having the specifications of a bead apex shown in Table 1 has a tire size of 215 / 60R.
Sixteen tires were prototyped, and the durability, steering stability (turning performance), and ride comfort (shock absorption) of the test tires were measured, and the measurement results are shown in the same table. In Table 1, Comparative Examples 2 and 3 were obtained by laminating two rubber members, and Examples 1 and 2 were laminated through a multilayer body.
Are each formed with a bead apex using an extruder, and specifications other than the bead apex are the same for each tire as shown in Table 2.

Durability: The test tire was rim size (6.5 J × 16), load 1300 kg, internal pressure (250
The tire was disassembled after traveling on a drum at a speed of 60 km / h under a speed of 60 kPa / km and traveling around 60000 km. In Table 1, "* 1"
Indicates that a cord loose occurs in the carcass near the outer end of the bead apex rubber, "* 2" indicates that a crack occurs at the outer end j1 of the lower layer B1, and "* 3" indicates that the core rubber C1 and the sheath rubber C2 Outside of the interface in the tire axial direction and at the intermediate height position j2
Indicates that a crack has occurred, and "* 4" indicates good without damage.

Driving stability (turning performance) and ride comfort (shock absorption): The test tire was subjected to an internal pressure (240 kP
a), vehicle (30J) based on rim size (6.5J × 16)
00cc; FR car) mounted on all wheels, steering stability (turning performance) is the turning maneuverability when the vehicle is running on a flat dry asphalt road surface, and the ride comfort (shock absorption) is
The shock absorption when the vehicle traveled over a protrusion having a height of 20 mm in actual vehicle running was determined by a 10-point method by sensory evaluation by a driver. The higher the number, the better and better the performance.

[0041]

[Table 1]

[0042]

[Table 2]

The tire of the present embodiment using the bead apex having a multilayer structure in the form of an annual ring has a higher turning performance than Comparative Example 3 in which the same rubber material is formed in two layers with the same distribution amount.
It was confirmed that a high improvement effect can be exhibited in all points of shock absorption and durability.

[0044]

Since the present invention is configured as described above,
The lateral rigidity, bead durability, and riding comfort of the tire can both be improved to a large extent.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a bead apex having an annual ring shape.

FIG. 3 is a perspective view of a multilayer body showing an example of a method of forming a ring-shaped bead apex.

FIG. 4 is a schematic sectional view showing an example of a spiral bead apex.

FIG. 5 is a longitudinal sectional view of a bead apex.

FIG. 6 is an explanatory view showing a method of forming a bead apex using an extruder.

FIG. 7 is a longitudinal sectional view of a bead apex formed by using an extruder.

FIG. 8A is a schematic diagram illustrating the bending rigidity by modeling FIG. 9B, and FIG. 8B is a schematic diagram illustrating the bending rigidity by modeling a bead apex of the present application.

9 (A) and 9 (B) are cross-sectional views showing a conventional bead apex.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 8 Bead apex 11 Main body part 12 Folded part 16, 16A, 16B Multilayer structure 21A to 22F, 22, 23 Rubber layer H, S Rubber material P Center of bead apex

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-175130 (JP, A) JP-A-5-124408 (JP, A) JP-A-7-149117 (JP, A) JP-A-3- 248903 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 15/00-15/06

Claims (3)

(57) [Claims] 1. A carcass having a main body extending from a tread portion to a bead core of a bead portion through a side wall portion, a carcass connected to the main body portion and turned around the bead core, and a main body portion of the carcass And a bead apex made of two or more rubber materials having different rubber hardness and extending outward in the tire radial direction from the bead core interposed between the bead apex and the bead apex. The rubber layer composed of each of the above rubber materials forms a multilayer structure in which the rubber layer is spirally laminated from the center of the bead apex to the outer peripheral surface of the bead apex, and furthermore, the lamination of the rubber layer from the center of the bead apex to the outer peripheral surface of the bead apex. Pneumatic tires with three or more. 2. The difference Hh-Hs between the JISA hardness Hh of the hardest rubber material and the JISA hardness Hs of the softest rubber material among the rubber materials forming the bead apex is as follows:
The pneumatic tire according to claim 1, wherein the temperature is two degrees or more. 3. The bead apex has a lamination number of 7 or more, and the bead apex is formed by a plurality of rubbers having different rubber hardnesses fed into a screw chamber accommodating a screw shaft of an extruder. The pneumatic tire according to claim 1, wherein the pneumatic tire is laminated by being twisted with rotation of the pneumatic tire.