JP2724291B2 - 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 the durability of a bead portion and reducing the weight of the bead portion.

[0002]

2. Description of the Related Art A carcass is formed of a steel cord.
For example, a heavy-duty tire for trucks and buses is deformed so as to protrude outward from the bead portion a to the sidewall portion b as shown in FIG. At this time, in the bead portion a, a large compressive force repeatedly acts on the winding portion c1 of the carcass c located outside the neutral line n of the stress, and as a result, looseness between the cord and the rubber occurs at the winding end. At the same time, this serves as a starting point to induce carcass separation, and the bead portion is likely to be damaged.

Therefore, conventionally, as shown in FIG. 8, by increasing the amount of rubber of the bead apex d, the cushioning property is improved by increasing the amount of rubber, so that the time required for loosening can be extended, and the bead core e can be prevented. Measures have been taken to increase the rigidity of the bead portion and reduce the amount of deformation itself by providing a bead reinforcing member f made of a cord layer on the inside and outside of the winding and winding portions c1.

[0004]

However, this method has a problem that heat generation is increased due to an increase in the volume of the bead portion. In particular, when the rubber amount of the bead apex is increased, the heat generation is not increased. In addition, since the wound portion c1 and each of the bead reinforcing members f are further away from the neutral line n, the applied compressive stress increases in reverse, and a remarkable improvement in bead portion durability cannot be expected. In addition, the weight of the tire increases with an increase in the volume, and fuel efficiency is impaired.

Accordingly, the present inventor has made various studies in view of such a situation. As a result, in the region Y between the upper adjacent point where the main portion of the carcass ply is close to the outer end point of the bead apex and the lower adjacent point where the carcass ply starts to separate from the bead core, as shown in FIG. In particular, the shape of the carcass center line j1 before filling with the internal pressure is largely convexly curved with a radius of curvature r along the bead apex; however, in the case of a heavy load tire having a standard internal pressure of 7 ksc or more, The shape of the center line j2 of the carcass should be substantially linearly elongated by a large tensile force due to high internal pressure; and the center line j3 of the carcass maintained a substantially linear shape even in a load state during rolling of the tire. And deforming so as to fall outward. Then, it was found that by forming the center line of the carcass before filling the internal pressure into a substantially straight line in advance, the deformation of the bead portion can be reduced while the volume of the bead apex is reduced.

That is, according to the present invention, the carcass ply center line in the region Y at the bead portion in a state where the internal pressure of 0.5 ksc is charged, that is, in a state where the tire is substantially formed in a vulcanization mold, Based on the fact that it is formed in a substantially straight line, it effectively increases the bead durability and
It is an object of the present invention to provide a heavy duty tire that can achieve weight reduction at a bead portion.

[0007]

In order to achieve the above object, the present invention provides a heavy duty tire according to the present invention, comprising: a main body portion extending from a tread portion to a sidewall portion to a bead core of a bead portion; A carcass comprising at least one carcass ply having a winding portion wound up from the inside in the tire axial direction to the outside and aligning steel carcass cords, and a portion between the main body portion of the carcass and the winding portion. A bead apex rubber extending in a tapered shape from the bead core toward the tire radially outward, and when the tire is mounted on a standard rim and filled with an internal pressure of 0.5 ksc, the tire is closest to the tire bore. An upper adjacent point P of the body portion of the carcass ply, which is close to a radially outer end point of the bead apex rubber. A ply center line in a region Y between the upper adjacent point P1 and the lower adjacent point P2 which is separated from the bead core is orthogonal to the straight line X having a length L connecting the upper adjacent point P1 and the lower adjacent point P2. The maximum deviation amount V in the direction of the movement is substantially linear, not more than 0.02 times the length L.

Preferably, the winding portion of at least one carcass ply extends radially outward from the bead apex rubber. At this time, in a region where the winding portion and the main body portion are adjacent to each other, the carcass cord of the main body portion is formed. Distance K between the wire and the carcass cord of the winding section
Is preferably in the range of 0.15 to 4.5 times the diameter D of the carcass cord.

[0009]

As described above, the center line of the ply in the body portion of the carcass ply is formed substantially linearly in the region Y, and the slack portion curved with the conventional radius of curvature r is eliminated. As a result, the code path of the carcass is shortened, so that the carcass is prevented from protruding outward during the standard internal pressure filling and when a load is applied, and the bead portion deformation itself is reduced.
In addition, since the carcass main body and the winding portion are close to each other by forming a substantially straight line, in addition to reducing the amount of rubber of the bead apex, the winding portion can relatively approach the neutral line n of the stress, Along with the reduction in the amount of deformation itself, the compression force acting on the winding portion can be significantly reduced.

Furthermore, since the use of the conventional bead reinforcing member f can be eliminated by reducing the amount of deformation of the bead portion itself, the amount of rubber in the bead apex can be reduced and the volume of the bead portion can be significantly reduced. Can be
Internal heat generation can be suppressed, and further improvement in bead portion durability can be achieved. It also helps to improve fuel economy by reducing the volume of the bead.

Further, since the region Y is a portion where a large distortion is generated when a load is applied, by avoiding this portion, the winding portion is terminated at a high point radially outside the bead apex rubber. It is possible to effectively suppress the generation of looseness between the cord and rubber starting from the winding end. At this time, in the adjacent area where the winding portion and the main body portion are adjacent to each other, the inter-cord distance K between the carcass cord of the main body portion and the carcass cord of the winding portion is regulated, and the shear force acting between the cords is reduced. is required.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a heavy load tire 1 (hereinafter referred to as a tire 1).
Shows a tire cross section in a state where the rim is assembled to a standard rim R which is a standard applicable rim such as JATMA, TRA, ETRTO and the like and filled with an internal pressure of 0.5 ksc. Note that the standard internal pressure means a pressure determined as, for example, a maximum air pressure in the above standard.

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 beads 4 and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2.

The carcass 6 includes a main body portion A extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the side wall portion 3 and a body portion A connected to the main body portion A and extending around the bead core 5 from the inside in the tire axial direction. It is formed from one or more carcass plies 9 having a winding portion B wound outward. A space between the main body portion A and the winding portion B of the carcass 6 is filled with a bead apex rubber 10 extending outward from the bead core 5 in the tire radial direction.

The bead core 5 is a ring body in which steel bead wires are continuously wound in multiple stages.
In this example, the cross-section is a flat hexagon having a long lateral direction, and the long axis of the bead is inclined inward in the tire axial direction at an angle of, for example, 15 degrees inward in the tire axial direction. By being arranged substantially parallel to the bottom surface 4S1,
The fitting force with the rim R is increased over a wide range over a light weight.

The bead apex rubber 10 is made of a relatively hard rubber having a JISA hardness of, for example, 50 to 80 degrees, and rises from the upper surface of the bead core 5 into a substantially triangular cross section. The bead apex rubber 10
For example, as shown by a dashed line in FIG.
The lower part 10B and the lower part 10B may be made of different rubbers, and the rubber hardness of the upper part 10A may be made smaller than the rubber hardness of the lower part 10B (soft rubber).

Further, the carcass ply 9 is formed by connecting the steel carcass cord 11 to the tire equator CO by 75 to 9%.
A code arrangement of a radial arrangement or a semi-radial arrangement aligned at an angle of 0 degrees, and this code arrangement is softer than the bead apex rubber 10, and if the bead apex rubber 10 has the two-layer rubber structure. Is covered with a softer topping rubber than the rubber of the lower portion 10B and is formed in a sheet shape. The winding portion B of the carcass 6 extends substantially in contact with the outer side surface of the bead apex rubber 10 and, in the portion in contact with the wound portion B, curves in a concave arc with a radius of curvature R4 having a center outside the tire.

In the bead portion 4, the main body portion A of the carcass 6 substantially contacts the inner surface of the bead apex rubber 10 in the tire axial direction, and the innermost one of the carcass plies 9 closest to the tire cavity H is provided. An upper adjacent point P1 at which the main body portion A9a of the carcass ply 9a is closest to the radially outer end point 13 of the bead apex rubber 10, and a lower adjacent point at which the main body portion A9a starts to separate radially outward from the bead core 5. In a region Y between the main body portion A9a and the ply center line J, the ply center line J of the main body portion A9a is formed substantially linearly in the state where the internal pressure is 0.5 ksc. In this example, the carcass 6 is formed from one carcass ply 9a, and therefore, the main body A9a is located at the upper adjacent point P
1 and substantially contacts the outer end point 13 and substantially separates from the bead core 5 at a lower adjacent point P2 as it substantially contacts the bead core 5 and extends outward in the tire radial direction.

Here, the ply center line J is a line passing through the center of the carker cord in the ply, and the substantially linear shape is, as shown in FIG. 3, the upper adjacent point P1 and the lower adjacent point P1.
2 means that the maximum deviation amount V from a straight line X having a length L that is perpendicular to the straight line X is less than or equal to 0.02 times the length L. Means that the deviation amount V is at least 0.055 times the length L.

As described above, since the ply center line J of the carcass ply 9a is substantially linear in the region Y, the code path of the carcass 6 is shortened, and when the standard internal pressure is filled, the load is further reduced. When loaded, 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 winding portion B relatively approaches the neutral line of the stress, thereby reducing the amount of deformation of the bead portion 4 and the winding portion. B
Can be greatly reduced. Therefore, in the present embodiment, the use of the conventional bead reinforcing member including the cord layer disposed around the bead core 5 and the inside and outside of the winding portion B is excluded.

The effect of reducing the bead deformation due to the linear shape is the tire width TW, which is the distance between the tire maximum width points 12, 12 at which the outer surface of the sidewall portion 3 projects outward most.
B between the outer surface 4S2 of the bead portion 4 and the bead width BW that is the distance between the bead heel points
It is suitably exerted on a tire having a W / TW of 0.69 to 0.96. This is because a tire having a ratio BW / TW of less than 0.69 has a profile of the bead portion 4 lying too far outward in the tire axial direction, and a tire having a ratio BW / TW of more than 0.96 has a It is considered that the profile becomes too large in the radial direction, and in any case, the effect of reducing the bead deformation is hardly remarkably exhibited.

If the deviation amount V exceeds 0.02 L on the convex side, that is, on the + side in FIG. 3, especially when a load of three times or more the standard load determined by JATMA or the like is applied, the bead portion and the rim flange are not crushed. The contact pressure with the part increases, and the durability of the bead part is significantly reduced. Also, the deviation amount V is concave,
That is, when the value exceeds 0.02 L on the negative side, the carcass cord tension is loosened, and the carcass cord is wavy at the buttress portion 20 and the tread crown portion on the tread side. To reduce the uneven wear resistance and the like.

When the internal pressure is 0.5 ksc,
In the tread portion 2, the ply center line J
An arc of a radius of curvature R1 having a center on the tire equatorial plane and an arc of a radius of curvature R2 having a center on a tire axial line Q passing through the maximum width point 12 in the sidewall portion 3. The lower portion has an arc-shaped profile with a radius of curvature R3 centered on the tire axial line Q. The arcuate portion of 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 each of the radiuses of curvature R1 to R4
Has a relationship such as the following equation (1). R1> R2 ≒ R3> R4 (1)

It is desirable that the arc portion having the radius of curvature R3 smoothly contacts the substantially linear portion at the upper adjacent point P, and this embodiment has this configuration. A portion radially outward from the upper adjacent point P is formed as an extended straight portion of the substantially linear portion, and if an attempt is made to make the extended straight portion and an arc portion having a radius of curvature R3 come into contact with each other, the extended portion is extended. In order to form a straight portion, it is necessary to provide a highly rigid reinforcing layer in a portion radially outward from the outer end point 13 of the bead apex rubber, or to increase the volume of rubber or the like, which increases the weight and It is not preferable because it causes an increase in heat generation. Further, by providing a reinforcing layer having high rigidity, a portion radially outside of the outer end point 13 of the bead apex rubber is formed as the extended linear portion, and the extended linear portion and the curvature radius R are formed.
When the configuration is such that the circular arc portion 3 is in contact, the position where the extended linear portion and the circular arc portion are in contact is substantially the same as the upper end position of the reinforcing layer, and stress tends to concentrate on the position portion during traveling. It may cause damage. Assuming that the arc portion having the radius of curvature R3 is in contact with the substantially linear portion at the position of the outer end point 13 of the bead apex rubber as in the present example, the point of contact with the upper end of the bead apex gradually tapering is positioned. Therefore, the concentration of stress can be minimized, and there is no need to provide extra rubber, so that the weight is reduced.

The radius of curvature R4 is the same as that of the winding portion B9a.
, The radius of curvature of the concave arc of the ply center line J is formed, and the winding-up portion B9a has a concave arc, whereby the volume reduction of the bead apex rubber 10 can be further ensured. Looseness generated between the side wall and the rubber can be prevented.

The bead apex height Hm, which is the height of the outer end point 13 of the bead apex rubber 10 from the bead base line 16, is
Is preferably 0.1 to 0.3 times the carcass height Hk, which is the height from the carcass 6 to the outer surface of the carcass 6 on the tire equator CO, and the bead apex height Hm is 0.1.
When it is less than Hk, the tire production becomes difficult, and the bead apex rubber 10 is too small, and the carcass 6 in the vicinity thereof is bent, so that defects such as air pools are easily generated, and the bent portion becomes a starting point. Induces breakage of the carcass cord during running. On the other hand, if the bead apex height Hm exceeds 0.3 Hk, the bead apex rubber 10 becomes excessively large, thereby deteriorating heat build-up, lowering durability and increasing weight. Therefore, more preferably, 0.2
5Hk or less, more preferably 0.20Hk or less. The bead base line 16 is the bead bottom 4
It means a tire axial line passing through the outer end in the tire axial direction of S1.

The curvature radius R3 is equal to the carcass height H.
k is preferably 0.75 to 1.15 times, and
If it is less than 75 times, the volume of the bead portion 4 becomes large,
As the weight of the tire increases, the heat generated during traveling increases and damage is liable to occur. Further, it is difficult to manufacture a tire having a size exceeding 1.15 times.

In addition, at least one carcass ply, in this example, the carcass ply 9a has a high turn-up winding structure in which a winding portion B9a projects radially outward from the outer end point 13 of the bead apex rubber 10. The hoisting height He of the hoisting end E from the bead base line 16 is set to be larger than the bead apex height Hm and below the tire maximum width point 12, that is, the amount of distortion when the hoisting portion B9a is loaded is relatively small. By terminating at the height position, the stress acting on the winding end E is reduced. In addition, the winding portion B9a has a main portion A of the carcass 6, and in this example, the carcass ply 9a.
The adjacent area 15 adjacent to the main body portion A9a is formed. At this time, as shown in FIG. 4, the inter-cord distance K between the carcass cord 11A of the adjacent main body part A9a and the carcass cord 11B of the winding part B9a in the adjacent area 15 is set to 0.1 mm of the diameter D of the carcass cord. 15-4.
The shear force acting between the carcass cords 11A, 11B is set to be five times as large as that of the carcass cords 11A, 11B.
It is relaxed by the elasticity of the rubber material interposed between B. When the inter-cord distance K is less than 0.15D, the effect of reducing the shearing force becomes insufficient, and sometimes the carcass cords 11A,
Cord loose occurs, such as partial contact of 1B. Therefore, more preferably, the inter-code distance K is 0.2
D or more, more preferably 0.4D or more. On the other hand, if the inter-cord distance K exceeds 4.5 D, the heat generation property is impaired and the weight is increased, for example, the volume of the bead portion is unnecessarily increased, and therefore, it is more preferably 3.0 D or less, still more preferably 2.0 D. It is as follows. The rubber material interposed between the cords may be a topping rubber of a carcass ply, or may be a rubber layer having a hardness substantially equal to that of a topping rubber separately provided between the carcass plies.

In addition to the present embodiment, as shown in FIG. 5, a plurality of, for example, two carcass plies 9 are provided.
a, 9b, wherein at least one carcass ply forms the high turn-up winding structure. When there is a carcass ply having a low turn-up winding structure, it is preferable to cover the low turn-up winding portion B9b with a winding portion B9a of an adjacent carcass ply 9a on the tire lumen side. When a plurality of adjacent areas 15 are formed due to the presence of a plurality of high-turn-up carcass plies, the distance K between cords in each adjacent area 15 is
The diameter is set to be 0.15 to 4.5 times the diameter D of the carcass cord.

In this embodiment, the tire maximum width position height H
At a point 19 on the tire outer surface which is separated from the bead base line 16 by a distance Ht that is 0.47 times the distance h from the bead base line 16, the thickness T from the tire outer surface to the carcass main body portion A and the outside of the bead. The ratio Ht / Hj to the distance Hj in the tire axial direction from the side surface 4S2 to the lowest point in the radial direction of the bead core 4 is in the range of 0.15 to 0.50. If the ratio Ht / Hj exceeds 0.50, the bead weight increases and the heat generation property is impaired. Conversely, if the ratio Ht / Hj is less than 0.15, the thickness T becomes too small to reduce the carcass cord loose. Easy to trigger.

In this embodiment, the belt layers 7 provided outside the carcass 6 are the first to fourth belt plies 2 arranged in order from the carcass 6 side toward the tread surface.
It has a four-layer structure consisting of 1, 22, 23 and 24. The ply width of the first belt ply 21 is substantially the same as the ply width of the third belt ply 23, and the ply width of the second belt ply 22, which is the maximum width, is set to 0.8 of the tread width.
By setting the ratio to 0 to 0.95 times, substantially the entire width of the tread portion 2 is reinforced with a tag effect. In addition, the fourth which becomes the minimum width
The belt ply 24 mainly functions as a breaker for protecting the inner first, second, and third belt plies 21, 22, and 23, improves cut-through resistance from the tread surface, prevents puncture, and the like. Prevents surface flaws from reaching the inside and growing.

Each of the belt plies 21 to 24 has a steel belt cord arranged in parallel with each other, and the first belt ply 21 applies the belt cord to the tire equator CO.
And the second belt ply 22 moves the belt cord in the same direction as the first belt cord and 14 to 2 with respect to the equator CO.
The third belt ply 23 has its belt cord disposed in the opposite direction to the second belt cord and at an inclination angle of 14 to 22 degrees with respect to the tire equator CO. As a result, the belt layer 7 forms a strong truss structure, imparts necessary belt rigidity to maintain steering stability, and suppresses a dimensional change of the tire.

[0033]

[Example] A heavy-duty tire having a tire size of 11R22.5 16PR and having a structure shown in FIGS.
The bead heat generation, bead durability, and tire weight of each test tire were compared.

The heat build-up of the bead was measured using a standard rim (2
2.5 × 8.25), a standard internal pressure (8.00 ksc), and a load (three times the standard load = 9,000 kg) on a rotary drum testing machine at a speed of 20 km / h and 10,000.
After traveling for km, the temperature of the bead portion was measured every 1000 km, and the average value of the measured temperatures was indexed with the conventional tire as 100. The smaller the index value, the lower the temperature and the better. Regarding the durability of the bead portion, the tire was disassembled after the 10,000 km running, and the presence or absence of cord loose in the carcass winding portion was confirmed. The tire weight is calculated as an index with the conventional tire being 100. The smaller the index value, the lighter and the better.

[0035]

[Table 1]

[0036]

Since the heavy duty tire of the present invention is constructed as described above, the durability of the bead portion can be effectively increased, and the weight of the bead portion can be reduced.

[Brief description of the drawings]

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

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

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 a schematic view of a bead portion showing another embodiment of a carcass.

FIG. 6 shows the results of conventional internal pressure filling and load application of a tire.
It is a schematic diagram explaining deformation of a carcass.

FIG. 7 is a schematic diagram illustrating bead deformation due to a load applied to a conventional tire.

FIG. 8 is a cross-sectional view illustrating the structure of a bead portion of a conventional tire.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 9, 9a, 9b Carcass ply 10 Bead apex 11, 11A, 11B Carcass cord 15 Adjacent area A, A9a Body part B, B9a Winding part H Tire bore J ply Center line

Claims (3)

(57) [Claims] 1. A steel body comprising: a main body extending from a tread portion to a side wall portion to a bead core of a bead portion; and a winding portion connected to the main body portion and winding up the bead core from inside to outside in the tire axial direction. A carcass composed of at least one carcass ply obtained by aligning carcass cords, and a bead apex rubber that extends from the bead core to the outside in the tire radial direction in a tapered shape, passing between the main body portion and the winding portion of the carcass. Equipped with the tires on the standard rim and 0.5
In a state where the internal pressure of ksc is charged, an upper adjacent point P1 of the body portion of the carcass ply closest to the tire cavity, which is close to a radial outer end point of the bead apex rubber.
A ply center line in a region Y between the upper adjacent point P1 and the lower adjacent point P2 which is separated from the bead core is orthogonal to the straight line X having a length L connecting the upper adjacent point P1 and the lower adjacent point P2. The maximum deviation amount V in the direction of the displacement is 0.02 of the length L.
A heavy duty tire characterized in that the tire has a substantially linear shape that is twice or less. 2. The carcass has at least one carcass ply in which a winding portion protrudes radially outward from an outer end point of the bead apex rubber to form an adjacent area in which the winding portion is adjacent to a main body portion. And the inter-cord distance K between the carcass cord of the main body part and the carcass cord of the winding part which are adjacent to each other in the adjacent area.
The heavy duty tire according to claim 1, wherein the diameter is 0.15 to 4.5 times the diameter D of the carcass cord. (3) Ply center of the carcass ply body
The line is centered on the tire axial line passing through the tire maximum width point.
Having an arc portion having a radius of curvature R3,
The substantially linear portion in the area Y is the upper adjacent point P
2. A smooth contact in the vicinity of 1.
Heavy duty tires.