JP3116044B2 - Pneumatic tires for heavy duty, light trucks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving bead durability while reducing weight at a bead portion.

[0002]

2. Description of the Related Art For example, a pneumatic tire for a heavy-duty or light-duty truck (hereinafter referred to as a pneumatic tire or a tire if necessary) which is a heavy-duty tire for a truck or a bus or a light-duty tire for a small truck. In order to maintain durability, conventionally, as shown in FIG. 4A, the rubber volume of the bead apex rubber b filled between the carcass body a1 and the winding portion a2 is increased to increase the bead rigidity. To reduce the tire deformation itself due to the applied load. The thickness t of the bead apex rubber b at this time is, for example, in a heavy load tire,
It reaches about 9 to 20 mm at the outer end position of the winding portion a2.

On the other hand, in recent years, the bead structure has been reviewed in order to reduce the weight of the tire. As shown in FIG. 4B, the volume and height of the bead apex rubber b are greatly reduced, and the bead apex rubber b is wound up. A technique has been proposed in which the portion a2 is raised to be close to the carcass body a1 to reduce the weight while maintaining bead durability.

[0004]

However, in the tire having such a structure, the carcass body a1 has a bead core c.
, The carcass is strongly pulled at the contact position cp between the carcass and the bead core c and stress is applied, and the carcass cord peculiar to this structure is easily broken.

In producing such tires,
Since the winding portion a2 of the carcass is sharply bent at the lower end position of the proximity area y, air accumulation is likely to occur in the vicinity bp of the outer end of the bead apex rubber b after vulcanization in order to return the winding portion a2. On the contrary, there is also a problem that bead durability is reduced.

Accordingly, the invention of claim 1 of the present application is directed to a first rubber layer interposed between the carcass and the bead core and the bead apex rubber, and a first rubber layer interposed between the carcass ply main body and the winding portion in the proximity area. Based on the provision of the second rubber layer, in addition to the breakage damage of the carcass cord, air accumulation near the outer end of the bead apex rubber can be suppressed and bead durability can be improved. It aims to provide tires.

[0007]

In order to achieve the above object, a bead which is folded back by the bead core and extends radially outward from the bead core is provided on a carcass ply body extending from the tread portion to the bead core of the bead portion through the sidewall portion. A carcass having a carcass ply having a winding portion extending along an apex rubber, and a belt layer disposed inside the tread portion and outside the carcass, and the winding portion of the carcass is provided with the bead. By passing over the outer end of the apex rubber, a proximity area close to the carcass ply body is formed, and the carcass has a thickness of 1.0 to 3.0 mm between the bead core and the bead apex rubber. The first rubber layer is interposed between the carcass ply main body and the winding-up portion and in the proximity area. Is interposed a second rubber layer of continuous addition thickness 2.0~6.0mm the first rubber layer, moreover the first and second rubber layer of, JISA hardness of 50 to 80
A pneumatic tire for a heavy-duty, light-duty truck, characterized in that the pneumatic tire is less than the JISA hardness of the bead apex rubber.

The first and second rubber layers are made of JISA
The hardness is 50 to 80 degrees and smaller than the JISA hardness of the bead apex rubber to suppress carcass cord breakage and suppress air accumulation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show a tire cross section in a 50 kpa internal pressure state in which a pneumatic tire 1 is assembled on a standard rim and filled with an internal pressure of 50 kpa. The standard rim means a standard rim defined by JATMA.

In the figure, a tire 1 has a tread 2
And a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at an inner end of each sidewall portion 3, and is formed as a heavy load tire in this example. . It may be a tire for a small truck. The tire 1 is reinforced by a toroidal carcass 6 extending between the beads 4 and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2.

In the present embodiment, the carcass 6 has a carcass cord made of an organic fiber such as polyester, rayon, nylon, or aromatic polyamide which is 75 to 9 with respect to the tire equator CO.
The carcass plies 29, 30 are arranged in one to three sheets, which are arranged at an angle of 0 degrees, in this example, two sheets.

The carcass ply 29 inside the bead core 5 extends from the tread portion 2 to the sidewall portion 3.
On both sides of the carcass ply main body 29A, the winding portion 29B is provided to turn the bead core 5 from the inside to the outside in the tire axial direction. The outer carcass ply 30 is placed on the carcass ply main body 29A and
B extends radially inward over B and has an inner end that terminates in an outer portion of the bead core 5 or a lower portion of the bead core. The carcass 6 may be constituted by a single carcass ply 9 in which steel carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire equator CO.

A space between the carcass ply main body 29A and the winding portion 29B is filled with a bead apex rubber 10 extending from the bead core 5 toward the tire radially outward.

The carcass 6 has a structure in which the carcass ply main body 29A is formed of the outer end 1 of the bead apex rubber 10.
3 and the carcass ply body 29
In a region Y between the position where A starts to separate radially outward from the bead core 5, the carcass ply main body 29A is formed substantially linearly in the state of the 50 kpa internal pressure.

Thus, the carcass ply body 29A
However, by forming a substantially straight line at least in the region Y, the code path of the carcass 6 is shortened, and when the standard internal pressure is filled, and further when a load is applied, the carcass 6 can be suppressed from protruding outward. The amount of deformation of the bead portion 4 itself can be reduced. Further, by forming the substantially straight shape, the thickness of the bead apex 10 is reduced, and the winding portion 29B relatively approaches the neutral line of the stress, thereby reducing the deformation amount of the bead portion 4 and the winding portion. The compression force acting on 9B can be greatly reduced.

On the other hand, the winding portion 29B of the carcass 6 has a high turn-up winding structure projecting radially outward from the outer end 13 of the bead apex rubber 10, and the protruding portion of the winding portion 29B is a carcass ply body. A proximity area 15 close to 9A is formed. This proximity area 1
The length L0 along the carcass 6 of No. 5 is in the range of 35 to 70 mm, thereby providing a necessary bead rigidity.

In the proximity area 15, the rubber thickness between cords between the carcass cord of the adjacent carcass ply body 29A and the carcass cord of the winding portion 9B is in the range of 0.5 to 4.0 mm in this example. The shear force acting between the carcass cords is reduced by the elasticity of the rubber material interposed between the cords.

In the present embodiment, the bead core 5 has a hexagonal cross section formed by the single wind. Therefore, it has a corner in the contact area 17 with the carcass ply 29,
Carcass cords may be broken.

As shown in FIG. 3, the bead core 5 can be of a so-called single-wind type in which a single rubberized bead wire is spirally wound in multiple layers. The bead core 5 has a flat hexagonal cross-sectional shape, and its long major axis is arranged substantially in parallel with a rim sheet inclined at an angle of, for example, 15 degrees, so that the bead core 5 is lightweight and has a wide area. The fitting force with the rim is increased.

However, since the bead core 5 has a polygonal shape, the corners thereof come into contact with the carcass 6, and the substantially linear ply body 9A is strongly pulled under a load. More likely to occur.

Therefore, the contact area 17 of the bead core 5 that contacts the carcass 6 is covered with the textile cloth 19.
As a result, the corners of the bead core 5 become smooth in an arc shape, thereby reducing the bending and contact pressure of the carcass 6, and
Direct contact between the carcass cord and the bead wire is prevented. As a result, breakage damage of the carcass cord can be effectively suppressed.

Here, the textile cloth 19 is a woven fabric using a yarn of an organic fiber such as nylon, rayon or polyester, and the yarn is slightly thinner than a tire cord, for example, 940 dtex / 2 to 1670 dtex / 2.
Thicknesses of the order can be suitably adopted.

The textile cloth 19 is wound around the bead core 5 one or more times, preferably two times, to cover the entire periphery of the bead core 5.
As a result, the corners can be smoothly and reliably covered and protected with a larger arc, and the effect of suppressing the cord breakage damage can be guaranteed, and the productivity can be increased. When a sheet body in which yarns are arranged in parallel instead of a woven body is used, a carcass cord enters between the yarns and the suppression effect cannot be achieved.

On the other hand, the bead apex rubber 10
Is made of rubber having a JISA hardness of, for example, 70 to 100 degrees, and the height h of the outer end 13 from the bead base line 16 is set to 15 mm above and below the rim flange height H.
(Range of H ± 15 mm). That is, it is set lower and smaller than the bead apex rubber 10 of the tire 1A. Therefore, at the time of vulcanization molding, air accumulation is more likely to occur near the outer end of the bead apex rubber 10.

In the bead apex rubber 10, the height h of the radially outer end 13 from the bead base line 16 is set to 0. 1 to 0.3
It can be reduced to twice the range, thereby reducing the rubber volume and reducing the weight.

When the height h is less than 0.1 × Hk, the tire production becomes difficult, and the bead apex rubber 10 is too small to provide the required bead rigidity. Of the carcass cord while the carcass cord is running is liable to be broken. On the other hand, if it exceeds 0.3 × Hk, the heat generation property is impaired, the durability is reduced, and an unnecessary weight increase is caused. Therefore, it is preferably 0.25 × Hk or less, more preferably 0.20 × Hk.
× Hk or less. The bead base line 16 is defined as a tire axial line (a rim diameter reference line) passing through the outer end of the bead bottom surface 4S1 in the tire axial direction.

In the tire 1, in order to suppress the air accumulation in addition to the breakage damage of the carcass cord, as shown in an enlarged view in FIG. 2, the first between the carcass 6 and the bead core 5 and the bead apex rubber 10. The second rubber layer 32 is interposed between the carcass ply main body 29A and the winding-up portion 29B in the proximity area 15.

More specifically, the first rubber layer 31 has a thickness of 1.0 to 1.0.
It has a thickness T1 of 3.0 mm, and covers the periphery of the joined body 33 of the bead core 5 and the bead apex rubber 10, that is, the bottom surface of the bead core 5 and both side surfaces of the bead apex rubber 10.

The second rubber layer 32 has a thickness of 2.0 to 6.0 m.
m, and has a thickness T2 of m and extends radially outward in the proximity area 15 continuously to the first rubber layer 31. In this example, the second rubber layer 32 is formed by overlapping both end portions of the rubber piece forming the first rubber layer 31 beyond the outer end 13 and extending outward in the radial direction. Therefore, the first and second rubber layers 31, 32 are formed with the same rubber composition.

The first rubber layer 31 smoothly covers at least the corners of the bead core 5 in an arc shape, thereby reducing the bending and contact pressure of the carcass 6 and preventing the carcass cord from directly contacting the bead wire. Breakage damage of the carcass cord can be effectively suppressed. In addition, since the entire circumference of the joined body 33 is covered with a uniform thickness, the carcass ply main body 29A in the region Y can maintain a linear shape.

The second rubber layer 32 enhances the adhesiveness between the carcass ply body 29A and the winding portion 29B during vulcanization molding and also allows the second rubber layer 32 itself to flow. It can be suppressed effectively. The second rubber layer 32 is formed by the carcass ply main body 29A and the winding portion 2.
9B is also reduced, so that the bead durability is further improved.

The length L1 of the second rubber layer 32 along the carcass 6 from the outer end 13 is preferably 5 to 15 mm, and the first and second rubber layers 31, 32 have a JISA hardness of 50 mm. Up to 80 degrees, Beada Apex Rubber JISA
It is better to be smaller than the hardness.

The thickness T1 of the first rubber layer 31 is 1.0
If less than mm, the effect of suppressing the breakage damage is not achieved,
If it exceeds 3.0 mm, the fitting force with the rim will be insufficient. Also, the thickness T2 of the second rubber layer 32 is less than 2.0 mm,
If the length L1 is less than 5 mm, the effect of suppressing air accumulation cannot be sufficiently obtained, and conversely, the thickness T2 and the length L1
Exceeds 6.0 mm and 15 mm, respectively, causing an unnecessary increase in weight.

The belt layer 7 of the tire 1B is composed of at least two belt plies 35A and 35B using a highly elastic belt cord such as a steel cord, and in this example, two belt plies 35A and 35B. Crossed.

In the pneumatic tire, the bead portion 4 is formed of the textile cloth 19 and the first and second rubber layers 3.
It is also possible to use both 1 and 32 for protection. The belt layer 7 includes at least two belt plies, in this example, first, second, third, and fourth belt plies 21 </ b> A to 21 </ b> A arranged in order from the carcass side toward the tread surface.
D, for example, the first belt ply 21A
Means that the belt cord is 50 to 70 with respect to the tire equator CO.
The second, third, and fourth belt plies 21B to 21D have belt cords arranged at an angle of about 10 to 30 degrees while being arranged at an angle of about degrees. In addition, the inclination direction of the cord with respect to the tire equator CO is different between the second and third belt plies 21B and 21C, thereby forming a strong truss structure, providing necessary belt rigidity and maintaining steering stability. At the same time, the dimensional change of the tire is suppressed. As the belt cord, for example, a highly elastic cord such as a steel cord is used.

[0036]

EXAMPLE A pneumatic tire for a heavy-duty, light-duty truck having a tire size of 7.00R16 and having the structure shown in FIGS. 1 and 2 was prototyped according to the specifications shown in Table 1, and the bead durability of each sample tire was measured. Were compared.

Bead durability: A test tire was tested on a rotary drum tester under the conditions of a standard rim (5.50 F × 16), a standard internal pressure (600 kpa), and a load (1100 kg).
The vehicle was run at a speed of 0 km / h, and the running times until bead damage occurred were compared. The complete run is 600 hours, and the longer the running time, the better.

[0038]

[Table 1]

[0039]

The pneumatic tire of the present invention is constructed as described above, so that the bead durability can be improved while reducing the weight at the bead portion.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a tire of the first invention.

FIG. 2 is an enlarged sectional view showing the bead portion.

FIG. 3 is a sectional view showing a bead core together with a textile cloth.

FIGS. 4A and 4B are cross-sectional views illustrating a bead portion of a tire for explaining a problem of the related art.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9, 29 Carcass ply 29A Carcass ply main body 29B Winding part 10 Bead apex rubber 13 Outside end of bead apex rubber 15 Close area 17 Contact area 19 Textile Cloth 31 first rubber layer 32 second rubber layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 15/00 B60C 15/06

Claims (2)

(57) [Claims] 1. A carcass ply body extending from a tread portion to a bead core of a bead portion through a sidewall portion and a winding portion extending along a bead apex rubber folded back by the bead core and extending radially outward from the bead core. A carcass having a carcass ply, and a belt layer disposed inside the tread portion and outside of the carcass. A carcass is formed in which a first rubber layer having a thickness of 1.0 to 3.0 mm is interposed between a bead core and a bead apex rubber. Between the ply body and the winding portion and in the vicinity of the first rubber layer and in the vicinity of the first rubber layer and having a thickness of 2.0 to Is interposed a second rubber layer of .0Mm, moreover the first and second rubber layer is 50 to the JISA hardness
A pneumatic tire for a heavy-duty, light-duty truck, wherein the pneumatic tire is 80 degrees and smaller than the JISA hardness of the bead apex rubber. 2. A height h of an outer end of the bead apex rubber from a bead base line is within a range of 15 mm above and below a flange height H of a rim on which a tire is mounted. Item 4. A pneumatic tire for heavy loads and light trucks according to item 3.