JP3410647B2 - Heavy duty tire - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a heavy-duty tire, such as a truck or a bus, in which a carcass is formed of steel cord, a carcass is conventionally filled between a ply body and a ply winding portion. By increasing the rubber volume of the bead apex rubber and increasing the bead rigidity, the bead durability was improved by reducing the deformation due to the applied load.

On the other hand, in recent years, the bead structure has been reviewed to reduce the weight of tires, and as shown in FIG. 6, the volume of the bead apex rubber b is reduced and the ply winding portion a1 is raised to increase the ply body. By adjoining the portion a2, it is possible to reduce the weight while maintaining the bead durability.

However, in producing such a tire, the carcass ply winding portion a1 having a steel cord is sharply bent at the lower end position of the adjacent portion y. As a result, the ply winding portion a1 tends to return, and after vulcanization, air is likely to be accumulated at the outer end point e of the bead apex rubber b, and conversely the bead durability is deteriorated.

Therefore, the present invention can relatively increase the molding pressure in the vicinity of the outer end point of the bead apex rubber during vulcanization molding, and effectively suppress the occurrence of air accumulation in the vicinity of the outer end point. The purpose of the present invention is to provide a heavy-duty tire capable of improving bead durability while reducing the load.

[0006]

In order to achieve the above object, the invention according to claim 1 of the present invention is a heavy duty tire.
A steel body having a ply body portion extending from the tread portion to the bead core of the bead portion through the sidewall portion and a ply winding portion that is continuous with the ply body portion and that winds up the bead core from the inside in the tire axial direction to the outside. A carcass consisting of one carcass ply in which carcass cords are arranged, an inner liner rubber layer forming a tire inner surface along the carcass, and a carcass ply from the bead core to the tire between the ply body and the ply winding part of the carcass. A heavy-duty tire comprising bead apex rubber that extends radially outward, wherein the carcass has a ply winding portion that projects radially outward from an outer end point of the bead apex rubber. The winding part is adjacent to the ply body over a length L0 of 35 to 70 mm. Cormorant has a neighboring region, and Bidoepe
From the bead baseline at the radially outer end of the
Do apex height Hm, car on tire equator CO
Height Hk from the bead base line on the outer surface of the residue is 0.1
To 0.3 times, and between the carcass and the inner liner rubber layer, a reinforcing layer extending inward and outward in the radial direction from the height position of the radially outer end point of the bead apex rubber is provided, and the reinforcing layer is also provided. Is made of hard rubber having a JIS A hardness of 60 to 70 degrees, and has a length L1 along the carcass of 25 to 45 mm and a thickness T1 of 1.5 to 2.
5 mm, and the reinforcing layer has a distance of 15% of the length L1.
The central region, which is vertically separated from the center of the reinforcing layer, is
It is characterized in that it is arranged according to the outer end point of the dope apex .

In the region Y between the upper adjacent point P1 where the ply body portion is close to the outer end point of the bead apex rubber and the lower adjacent point P2 where the ply body portion starts to separate from the bead core, the ply center line is substantially straight. The shape is more preferable from the viewpoint of bead durability against a load and weight reduction by reducing the volume of the bead apex rubber.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a heavy-duty tire 1
The tire section (hereinafter referred to as tire 1) is assembled to a standard rim and an inner pressure state of 50 kpa filled with an inner pressure of 50 kpa is shown. Standard rims are standard rims specified by JATMA, "Design Rim" specified by TRA,
Or it means "Measuring Rim" specified by ETRTO.

The tire 1 includes a tread portion 2, 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. The tire 1 is reinforced by a toroidal carcass 6 extending between the bead portions 4 and 4, and a belt layer 7 arranged radially outside the carcass 6 and inside the tread portion 2.

The carcass 6 is formed from 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. The carcass ply 9 is formed from the tread portion 2. On both sides of the ply body 9A extending from the side wall part 3 to the bead core 5 of the bead part 4, ply winding parts 9B for winding the bead core 5 from the inner side to the outer side in the tire axial direction are provided.

Further, the carcass 6 is adjacent to the inner liner rubber layer 8 forming the tire inner surface Ts by extending between the bead portions 4 and 4 along the ply body portion 9A and the ply body portion 9A. A bead apex rubber 10 is provided between the bead core 5 and the ply winding portion 9B so as to taper from the bead core 5 toward the outer side in the tire radial direction.

In this example, the bead core 5 has a flat hexagonal cross-sectional shape, and the long major axis is, for example, 15
By being arranged substantially parallel to the bead bottom surface 4S1 which is inclined inward in the radial direction toward the tire axial direction inward with a degree angle, the fitting force with the rim is enhanced in a lightweight and wide range. .

The bead apex rubber 10 is J
The bead apex height Hm from the bead baseline 16 at the radially outer end point 13 of the relatively hard rubber having an ISA hardness of, for example, 50 to 80 degrees is the bead baseline 16 on the outer surface of the carcass 6 on the tire equator CO. The carcass height Hk is reduced to 0.1 to 0.3 times. As a result, the rubber volume is reduced and the weight is reduced. The bead apex height Hm is 0.1 x H
When it is less than k, tire production is difficult and bead rigidity is not imparted. On the other hand, if it exceeds 0.3 × Hk, heat generation is impaired, durability is lowered and unnecessary weight increase is caused. Therefore,
It is preferably 0.25 × Hk or less, more preferably 0.20 × Hk or less. Bead baseline 1
6 means a tire axial direction line passing through the tire axial direction outer end of the bead bottom surface 4S1.

In the present embodiment, the ply body 9A has an upper adjacent point P1 at which the ply body 9A is closest to the outer end point 13 of the bead apex rubber 10, and the ply body 9A is radiused from the bead core 5. In the region Y between the lower adjacent point P2 which starts to separate toward the outside in the direction,
The ply center line J of the ply body 9A is 50 k
It is formed in a substantially straight line in the internal pressure state of pa.

Here, the ply center line J is a line passing through the center of the carca cord in the ply, and the substantially straight line shape is, as shown in FIG. 3, the upper adjacent point P1 and the lower adjacent point P.
It means that the maximum deviation amount V in the direction orthogonal to the straight line X having a length L3 connecting with the line L is not more than 0.02 times the length L3.

As described above, since the ply body 9A has a substantially linear shape in the region Y, the cord path of the carcass 6 is shortened, and when the standard internal pressure is filled,
Furthermore, when a load is applied, the carcass 6 can be prevented from protruding outward, and the amount of deformation of the bead portion 4 itself can be reduced. Further, by forming the substantially linear shape, the thickness of the bead apex 10 is reduced, and the ply winding portion 9B relatively approaches the neutral line of stress, and the bead portion 4 is formed.
In addition to the effect of reducing the deformation amount itself, the compressive force acting on the ply winding portion 9B can be greatly reduced.

The effect of reducing the amount of bead deformation due to the substantially linear shape is that the tire width TW is the distance between the tire maximum width points 12, 12 that the outer surface of the side wall portion 3 projects outwardly.
And the bead width BW which is the distance between the outer side surfaces 4S2, 4S2 of the bead portion 4 or the distance between the bead heel points B
It is suitably exhibited in a tire having W / TW in the range of 0.69 to 0.96. This is because the tire having a ratio BW / TW of less than 0.69 has the profile of the bead portion 4 lying too far in the axial direction of the tire, and conversely a tire having a ratio BW / TW of more than 0.96 has It is considered that the profile becomes too sharp in the radial direction, and the effect of reducing the amount of bead deformation cannot be significantly exhibited in either case.

When the deviation amount V exceeds ± 0.02 × L3, it is difficult to obtain the effect of reducing the bead deformation amount due to the linear shape, but in addition, it is 0 on the + side (convex side in FIG. 3). ．
When it exceeds 02 × L3, especially when a load of 3 times or more of the standard load determined by JATMA or the like is applied, the contact pressure between the bead portion and the rim flange portion increases, and the durability of the bead portion remarkably decreases. On the other hand, when it exceeds 0.02 × L3 in the negative side, the tension of the carcass cord becomes loose and the carcass cord is finished wavy at the buttress portion 20 and the tread crown portion on the tread side. It adversely affects the tire profile at the time and reduces uneven wear resistance and the like.

In the internal pressure state of 50 kpa, the ply center line J extends in the tread portion 2 in an arc having a radius of curvature R1 centered on the tire equatorial plane, and at the side wall portion 3. , The maximum width point 1
Radius of curvature R centered on the tire axial direction line Q passing through 2
It has a profile curved in two arcs, and in the lower part, an arc having a radius of curvature R3 centered on the tire axial direction line Q. The arcuate portion having the radius of curvature R3 and the substantially linear portion in the region Y are smoothly joined in the vicinity of the upper adjacent point P1, and the respective radiuses of curvature R1 to R3 are R1>
It has a relationship of R2 and R3 .

The radius of curvature R3 is equal to the carcass height H.
It is preferably 0.75 to 1.15 times the value of k.
If it is less than 75 times, the volume of the bead part 4 becomes large,
As the tire weight increases, more heat is generated during running and damage is more likely to occur, and it is difficult to manufacture a tire that exceeds 1.15 times.

On the other hand, the ply winding portion 9B of the carcass 6
Has a high turn-up winding structure that protrudes outward in the radial direction from the outer end point 13 of the bead apex rubber 10, and the protruding portion of the ply winding portion 9B forms an adjacent area 15 adjacent to the ply body portion. This adjacent area 1
The length L0 along the ply of 5 is in the range 35-70 mm, which gives the required bead rigidity.

In the adjacent area 15, the carcass cords 11A and the ply hoisting portions 9 of the adjacent ply body portions 9A.
The inter-cord distance K between the B carcass cord 11B and
As shown in FIG. 4, the carcass cord has a diameter D of 0.15.
The shear force acting between the cords 11A and 11B is relaxed by the elasticity of the rubber material interposed between the cords 11A and 11B. When the inter-cord distance K is less than 0.15 × D, the effect of relaxing the shearing force becomes insufficient, and when it exceeds 4.5 × D, the volume of the bead portion 4 is unnecessarily increased and heat generation is impaired. In addition, it causes an increase in weight.

The bead apex height Hm is
Since the ply body 9A is reduced to a range of 0.1 × Hk to 0.3 × Hk and the ply body 9A is substantially linear, the ply winding portion 9B is located at the lower end position of the adjacent area 15 (the position of the outer end point 13). Bend sharply. The radius of curvature R of this bend
In this example, 4 is 20 mm or less, for example, about 10 mm. Therefore, in order to suppress air accumulation in the vicinity of the outer end point 13 of the bead apex rubber 10 due to this bending, between the carcass 6 and the inner liner rubber layer 8, the radial direction from the height position of the outer end point 13 is increased. A reinforcing layer 21 extending inside and outside is provided.

The reinforcing layer 21, as shown in FIG.
The SA hardness is made of hard rubber having a degree of 60 to 70 degrees, the length L1 along the carcass is 25 to 45 mm, and the thickness T1 is 1.5.
~ 2.5 mm.

The reinforcing layer 21 exhibits the following operational effects. That is, as shown in FIG. 5, when the raw cover body 1A for tire molding is formed, the reinforcing layer is provided between the carcass 6 and the inner liner rubber layer 8 and at the height position of the outer end point 13 of the bead apex rubber 10. 21 is interposed. At this time, since the inner liner rubber layer 8 has a constant thickness, the protrusion 22 that protrudes inward at the position of the reinforcing layer 21 on the inner surface Ts of the tire and corresponds to the thickness T1.
Is formed. Therefore, by pressing the tire inner cavity surface Ts of the green cover body 1A with the bladder in the vulcanization mold, the molding pressure at the protruding portion 22 can be relatively increased. As a result, the air that tends to accumulate in the vicinity of the outer end point 13 is effectively released to the outside, and a high-quality tire in which air accumulation is eliminated can be easily manufactured with high yield. After the vulcanization molding, the protrusion 22 has a reduced amount of protrusion due to the expansion of the inner liner rubber layer 8 and becomes smooth.

Further, the reinforcing layer 21 can increase the bead rigidity together with the ply winding portion 9B, and in particular relaxes the rigidity step in the vicinity of the outer end point 13, so that it is useful for further improving the bead durability.

If the JISA hardness is less than 60 degrees, the reinforcing layer 21 itself is thinly deformed by the pressure of the bladder and the molding pressure cannot be increased. If it exceeds 70 degrees, the rigidity difference becomes remarkable, and the upper end position of the reinforcing layer 21. It is easy to cause a failure. If the thickness T1 is less than 1.5 mm, a sufficient increase in molding pressure cannot be obtained, and the length L1 is 25 mm.
If it is less than the above, the pressing force becomes too local, and the air discharging effect is not exhibited. Conversely, the thickness T1 is 2.5 m
If it exceeds m, a rigidity step becomes conspicuous and a failure is likely to occur at the upper end position of the reinforcing layer 21. The length L1 is 45m
If it exceeds m, further improvement of the air discharge effect is not expected, and the weight and cost are unnecessarily increased.

The reinforcing layer 21 has a central region 21 vertically separated from the center of the reinforcing layer 21 by a distance of 15% of the length L1 in order to more effectively exert the air discharging effect.
A is arranged according to the outer end point 13 .

The belt layer 7 is composed of at least two belt plies, in this example, first, second, third and fourth belt plies 31A to 31D which are sequentially arranged from the carcass side toward the tread surface. In the first belt ply 31A, for example, the belt cords are arranged at an angle of about 50 to 70 degrees with respect to the tire equator C, and the second belt ply 31A
The third and fourth belt plies 31B to 31D are 10 to 30.
Belt cords are arranged at an angle of about a degree. The second and third belt plies 31B and 31C have different cord inclination directions with respect to the tire equator CO, thereby forming a strong truss structure and imparting necessary belt rigidity to maintain steering stability. At the same time, the dimensional change of the tire is suppressed. As the belt cord, a highly elastic one such as steel cord is used.

[0030]

[Specific example] A heavy-duty tire having a tire size of 11R22.5 14PR and having the configuration shown in FIGS.
The amount of air accumulated at the outer end point of the bead apex rubber of each test tire was compared.

Amount of air accumulation: The height h of the air accumulation at the outer end point shown in FIG. 6 was measured at four points on the tire, and the average value thereof was used for evaluation.

[0032]

[Table 1]

[0033]

Since the heavy duty tire of the present invention is constructed as described above, it is possible to relatively increase the molding pressure in the vicinity of the outer end point of the bead apex rubber, and to collect the air in the vicinity of the outer end point. The bead durability can be improved while effectively suppressing the occurrence of the phenomenon.

[Brief description of drawings]

FIG. 1 is a sectional view of a right half of a tire showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a bead portion thereof.

FIG. 3 is a schematic view of a bead portion for explaining a substantially linear state of a ply center line J.

FIG. 4 is a cross-sectional view of a carcass in an adjacent area for explaining a distance between cords.

FIG. 5 is an enlarged cross-sectional view showing a bead portion in the green cover body for explaining the function and effect of the reinforcing layer.

FIG. 6 is a cross-sectional view illustrating a bead portion of a tire for explaining the problems of the conventional technique.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead section 5 bead core 6 carcass 8 Inner liner rubber layer 9 Carcass ply 9A ply body 9B ply winding section 10 bead apex rubber 11A, 11B car cascode 13 Bead apex rubber outer end points 15 adjacent area 21 Reinforcing layer Ts Tire inner surface J-ply center line

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 15 / 00,15 / 06 B29D 30/06-30/36

Claims (2)

(57) [Claims] 1. A ply body extending from a tread portion to a side wall portion to a bead core of a bead portion, and a ply winding portion connected to the ply body portion for winding the bead core from an inner side to an outer side in a tire axial direction, A carcass consisting of one carcass ply in which steel carcass cords are arranged, an inner liner rubber layer that forms a tire inner surface along the carcass, and the carcass through the space between the ply body and the ply winding part. A heavy-duty tire comprising a bead apex rubber that extends in a tapered shape from a bead core toward a tire radial direction outer side, wherein the carcass has a ply winding portion protruding radially outward from an outer end point of the bead apex rubber. By this ply winding part, the ply body part and 35-70
bead baes having adjoining regions adjacent to each other over a length L0 of mm and at the radially outer end points of the bead apex.
The bead apex height Hm from the spline
From the bead baseline on the outer surface of the carcass on the equator CO
The height is in the range of 0.1 to 0.3 times, and between the carcass and the inner liner rubber layer,
A reinforcing layer extending inward and outward in the radial direction from the height position of the radial outer end point of the bead apex rubber is provided, and the reinforcing layer is made of hard rubber having a JISA hardness of 60 to 70 degrees, and has a length L1 along the carcass. 25-45m
m and the thickness T1 is 1.5 to 2.5 mm, and the reinforcing layer has a distance of 15% of the length L1.
Center the area above and below the center of the bead ape
A heavy-duty tire characterized by being arranged according to the outer end point of the box. 2. The bead portion is mounted on a standard rim to form a rim and is filled with an internal pressure of 50 kpa.
In the kpa internal pressure state, an upper adjacent point P1 of the ply body portion near the radially outer end point of the bead apex rubber and a lower adjacent point P of the ply body portion that starts to separate from the bead core.
The center line of the ply in the region Y between 2 and 2 is the upper adjacent point P
The maximum deviation amount V in the direction orthogonal to the straight line X from the straight line X having the length L3 connecting 1 and the lower adjacent point P2 is the length L.
3. The heavy-duty tire according to claim 1, wherein the heavy-duty tire has a substantially linear shape that is 0.02 times or less than No. 3.