JPH0966711A - Heavy load radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a bead part while improving rim assembling performance and rim shift resisting performance. SOLUTION: In a loading condition X in which a tire is loaded in a rim J, the inner diameter ϕBC of the radial direction innermost end of a bead core 6 is set lower than the inner diameter ϕBT of a heel point 13 as a crossing point between the extended surfaces of a bead base surface 10 and the rising surface of the rim J in contact with a flange.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can improve the rim assembly performance and the rim displacement resistance performance, increase the durability of the bead portion by reducing the occurrence of damage such as ply loose, and reduce the tire weight. Also useful for heavy duty radial tires.

[0002]

2. Description of the Related Art Generally, a 15 ° taper rim defined as a 15 ° deep rim according to JATMA, JIS, etc., forms a rim seat surface on which a bead base surface of a tire is seated at an angle of 15 ° with respect to a tire axial direction line. It is tilted at.

In such a 15 ° taper rim, after the tire is assembled on the 15 ° taper rim, the bead base surface is moved along the rim seat surface toward the larger rim diameter by filling the internal pressure. Since it is possible to make a strong contact between the tire and the rim, for example, high internal pressure,
It is often used in heavy-duty tires for trucks and buses that are used under heavy loads.

Heavy-duty tires are usually used under the condition that they are largely flexed by 15% or more. Therefore, they are required to have high structural durability in the bead portion as compared with tires in other fields.

Therefore, the bead portion of the heavy duty tire is
It is reinforced with hard rubber and bead filler to increase its rigidity and reduce distortion due to bending.

However, if the rigidity of the bead portion is increased, deterioration of the rim assembly performance is unavoidable, and the fitting force with the rim tends to be insufficient, which adversely affects the rim displacement resistance performance.

[0007] In order to solve such problems,
Japanese Unexamined Patent Publication (Kokai) No. 5-185811 proposes to incline the bead base surface of the tire slightly more than the rim sheet surface of the rim.

[0008]

However, the above-mentioned proposal can improve the rim assembling performance and the fitting force with the rim to improve the rim displacement resistance performance. In the case of a large deformation, there is a tendency to induce ply loose in the carcass, the bead filler, etc., which may conversely reduce the durability of the bead portion.

The present inventor has conducted earnest research to improve the durability of the bead portion, the rim assembly performance, and the rim shift resistance performance, which are in a trade-off relationship, in a balanced manner. By regulating the position of the bead core arranged in the rim, it is possible to suppress the ply loose and improve the durability of the bead part, and also find that the rim assembly performance and the rim displacement resistance performance can be improved together, and the present invention has been completed. It was.

That is, the present invention is based on the fact that the inner diameter φBC of the innermost end of the bead core in the radial direction when mounted on the rim is set to be equal to or less than the inner diameter φBT of the heel point of the bead portion, thereby improving the rim assembly performance and the rim displacement resistance performance. In addition, the rigidity of the bead part can be maintained even if the conventional bead filler is removed, the durability of the bead part can be improved by reducing the occurrence of ply loose, and the radial tire for heavy load that is also useful for reducing the tire weight It is intended to be provided.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a folding portion is provided in a main body portion extending from a tread portion to a sidewall portion to a bead core of a bead portion so as to fold around the bead core from an inner side in an axial direction of a tire to an outer side. A heavy-duty radial tire equipped with a carcass and a belt layer arranged inside the tread portion and outside in the radial direction of the carcass, which is mounted on a deep rim of 15 °, wherein the bead core is mounted on the rim. The inner diameter φBC of the radially innermost end is the intersection of each extension surface of the bead base surface and the rising surface in contact with the rim flange in the bead portion in a mounted state in which the shape-retaining internal pressure of 0.5 ksc is filled. The inner diameter of the heel point is φBT or less.

When the rim is not mounted, the bead base surface of the bead portion inclines outward at an angle θ with respect to the tire axial direction, and the outside in the tire axial direction is radially outward, and this angle θ Is 1.0 of an angle α at which the rim seat surface of the rim on which the bead base surface is seated is inclined outward and upward.
It is desirable to be more than twice and less than 1.9 times.

In the mounted state, the bead core has a flat portion on the bottom side facing the rim seat surface, the flat portion being substantially parallel to the rim seat surface, and the inner end of the flat portion in the tire axial direction and the heel point. The length BP in the tire axial direction between and is preferably 1.3 times or more and 2.1 times or less of the total width BW of the bead core in the direction parallel to the rim sheet surface.

Further, a straight line connecting a lower adjacent point P2 where the carcass body starts to separate from the bead core and an intersection P3 where a radial line passing through the inner end of the plane portion in the axial direction of the tire intersects the carcass body. The angle β formed with the tire axial line is preferably 45 ° or more and 60 ° or less.

Further, in the region Y between the upper adjacent point P1 where the main body of the carcass contacts the outer end point of the bead apex rubber and the lower adjacent point P2 which starts to separate from the bead core, the main body is formed substantially linearly. Is desirable.

With the tire mounted on the rim, the inner diameter φBC of the innermost end of the bead core in the radial direction is set to be equal to or less than the inner diameter φBT of the heel point of the bead portion. Therefore, the bead core should be brought close to the rim seat surface of the rim. One can increase the tightening margin of the rubber, reduce the movement of the carcass around the bead core, the movement of the rubber to reduce the deformation of the bead part under a large load, reduce the risk of ply loose, and as a result,
The durability of the bead portion can be greatly improved, and the weight of the tire can be reduced by removing the bead reinforcing layer.

By setting the difference between the inner diameter φBC and the inner diameter φBT to be 2 mm or more, the deformation of the bead portion can be effectively reduced and the toe portion of the bead portion can be prevented from rising, but the radius of the bead core can be prevented. In order to prevent the carcass passing inward in the direction from being exposed from the bead base surface, the shortest distance between the carcass and the rim seat surface is 1.
It is desirable to keep at least 5 mm.

When the inclination angle θ of the bead base surface when the rim is not mounted is set to 1.0 times or more and 1.9 times or less of the inclination angle α of the rim seat surface, the bead is secured while ensuring the rim assembly performance. The portion can be firmly brought into contact with the 15 ° deep rim, and the fitting force with the rim can be increased to improve the rim displacement resistance performance. If the angle θ is smaller than 1.0 times the angle α, the fitting force with the rim cannot be sufficiently increased, and the rim displacement resistance cannot be effectively improved, while conversely, it is 1.9 times or more. If it is too large, the bead portion must be excessively compressed during the rim assembly, which adversely affects the rim assembly performance. Therefore, the angle θ is 1.0 to 1.9 of the angle α.
By more preferably 1.2 times or more and 1.9 times or less, both the rim assembly performance and the rim displacement resistance performance can be improved in a well-balanced manner.

Further, in the invention of claim 3, in the mounted state, when the bead core has a flat portion on its bottom side which is substantially parallel to the rim sheet surface, the bead portion is stably provided by the flat portion of the bead core. It can be assembled to the rim, the rim displacement resistance can be improved, and the generation of ply loose inside the bead core can be effectively suppressed.
It can improve durability.

Furthermore, the length BP in the tire axial direction between the inner end of the plane portion in the tire axial direction and the heel point is 1.3 times or more the total width BW of the bead core in the direction parallel to the rim seat surface and 2 Since it is less than 1 time, the bead base surface of the bead part can be pressed against the rim seat surface with a substantially uniform fitting pressure, and in addition to the improvement of rim assembly performance and rim displacement resistance performance, the local bead part It is possible to reduce the ply loose due to the specific stress and improve the durability, to optimize the inclination of the bead portion of the carcass, and to reduce the thickness of the bead portion to reduce the heat generation of the bead portion.

If the length BP is less than 1.3 times the full width BW, the toe part of the bead part may float when a large load is applied, and conversely if it is greater than 2.1 times. It becomes difficult to obtain the effect of reducing the deformation of the bead portion.

Further, in the invention of claim 4, the lower adjacent point P2
Angle β formed by the straight line connecting the intersection point P3 and the intersection point P3 with the tire axial direction line
Is 45 ° or more and 60 ° or less, the inclination of the carcass can be brought closer to the carcass line at the time of filling with internal pressure, the rubber thickness of the bead portion can be reduced, and the heat generation thereof can be reduced to prevent damage.

If the angle β is smaller than 45 °, the bead core excessively shifts inward in the tire axial direction, and the thickness of the rubber of the bead core at the bead portion in the axial direction of the tire becomes excessive, resulting in heat generation. On the other hand, if the angle is greater than 60 °, on the contrary, the thickness of the rubber inside the bead core in the tire axial direction becomes too large, which is not preferable.

Further, in the invention of claim 5, in the region K between the upper adjacent point P1 and the lower adjacent point P2 where the carcass main body is in contact with the bead apex rubber outer end point, the carcass main body is made substantially linear. At the time of forming, the cord path of the carcass becomes the shortest and approaches the carcass line when a load is applied, so that the carcass can be prevented from protruding outward during a load, and the amount of deformation of the bead portion itself can be reduced. In addition, since the carcass main body portion and the folded portion are close to each other by forming a substantially linear shape, the amount of rubber of the bead apex can be reduced and the folded portion can be relatively close to the stress neutral line, so that the deformation amount can be reduced. Along with the reduction of itself, the compressive force acting on the folded portion can be greatly reduced. Furthermore, by reducing the amount of deformation of the bead portion itself, the use of a conventional bead reinforcing member can be eliminated and eliminated, so that the amount of rubber in the bead apex can be reduced and the volume of the bead portion can be greatly reduced. Further, the internal heat generation can be suppressed and the bead portion durability can be further improved.

As described above, in the heavy duty radial tire of the present invention, the above-mentioned constitutions are organically combined and integrated so that the rim assembly performance and the rim displacement resistance performance are improved, and the ply loose is prevented. In addition, the durability of the bead portion can be increased, and it is also useful for reducing the weight of the tire and reducing the heat generation of the bead portion.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a mounted state X in which the heavy duty radial tire 1 of the present invention is mounted on a 15 ° deep rim J defined by JIS and filled with a shape-retaining internal pressure of 0.5 ksc.

The heavy-duty radial tire 1 comprises a pair of left and right bead portions 2, a sidewall portion 3 extending outward from each bead portion 2 in the radial direction, and a tread portion 4 connecting between the upper ends of the sidewall portions 3. It has a toroidal shape. Further, in the heavy duty radial tire 1, the main body portion 5A extending from the tread portion 4 to the side wall portion 3 to the bead core 6 of the bead portion 2 is provided with the folding portion 5B which is folded around the bead core 6 from the inner side to the outer side in the tire axial direction. The carcass 5 is provided, and a belt layer 7 that tightly tightens the carcass 5 is provided inside the tread portion 4 and outside the carcass 5 in the radial direction.

In the belt layer 7, the innermost belt ply 7A obtained by inclining the steel cord to the tire equator C at an angle of, for example, about 60 ± 10 ° and the steel cord to the tire equator C are used in this example. The belt plies 7B, 7C, and 7D that are inclined and arranged at a small angle of 30 ° or less are laminated in four layers such that the steel cords intersect each other.

Further, as shown in FIG. 2 in which the bead portion 2 is in a non-mounted state Y in which the tire is not mounted on the rim, the bead base surface 10 of the bead portion 2 has a tire axial direction with respect to the tire axial direction line L. Angle θ upwards outward with radial outwards
And the angle θ is
The range of 1.0 times or more and 1.9 times or less, and more preferably 1.2 times or more and 1.9 times or less, of the angle α at which the rim seat surface J1 of the 15 ° deep rim J on which 0 is seated is inclined upward and outward. Is set to.

Further, the bead core 6 is formed in a hexagonal cross section for carrying a high load, and is in the mounted state X.
In the above, the bottom surface facing the rim sheet surface J1 is provided with a flat surface portion 11 that is substantially parallel to the rim sheet surface J1.

Further, the bead portion 2 is a rim flange J2.
Of the bead base surface 1 and the extension surface of the rising surface 12 that contacts the
The length BP in the tire axial direction from the heel point 13 which is the intersection with the extension surface of 0 to the inner end 11A in the tire axial direction of the flat surface portion 11 is the whole length of the bead core 6 oriented parallel to the rim seat surface J1. It is set in the range of 1.3 times or more and 2.1 times or less of the width BW.

In the mounted state X, the inner diameter φBC of the radially innermost end 6a of the bead core 6 is set to be equal to or less than the inner diameter φBT of the heel point 13, and more preferably, equal to or less than the value obtained by subtracting 2 mm from the inner diameter φBT. .

The carcass 5 is made of nylon, rayon,
Consists of one or more carcass plies of radial or semi-radial structure in which organic fibers such as polyester and aromatic polyamide or steel cords are arranged at an angle of 70 to 90 ° with respect to the tire equator C and arranged with a topping rubber. In this embodiment, one carcass ply 5a in which the steel cord is inclined at an angle of 90 ° with respect to the tire equator C
And the main body 5A of this carcass 5
A bead apex rubber 9 having a substantially triangular cross-section that is tapered outward from the bead core 6 in the radial direction is disposed between the and the folded portion 5B.

The body portion 5A of the carcass 5 is substantially in contact with the inner side surface of the bead apex rubber 9 in the tire axial direction. In this example, the body portion 5A starts to separate from the bead core 6 at a lower adjacent point P2. And a straight line 15 connecting a radial line LR passing through the inner end 11A of the plane portion 11 in the tire axial direction and an intersection point P3 intersecting with the main body portion 5A forms an angle β with the tire axial direction line L of 45 ° or more and 60 ° or more. ° The range is set below. This is this angle β and the full width BW
This is because it was confirmed by experiments that there is a negative correlation between the ratio BP / BW of the length BP and the ratio BP / BW, and in the range of 45 ° to 60 °, the main body portion 5A has a negative correlation. It is possible to make the inclination close to the carcass line at the time of filling with internal pressure.

Further, in this example, as shown in FIG. 4, the main body portion 5A has a radially outer end point 9 of the bead apex rubber 9.
In the region K between the upper adjacent point P1 which is in contact with E and the lower adjacent point P2, the carcass line of the main body portion 5A, that is, the carcass center line in the main body portion 5A exhibits a substantially linear shape in the mounting state X. ing. It should be noted that, as shown in the same figure, the term “substantially linear” means that a maximum deviation amount V in a direction orthogonal to the straight line N from a straight line N having a length M connecting the upper adjacent point P1 and the lower adjacent point P2 This means that the length M is 0.02 times or less, and the conventional tire has an arc shape in which the deviation amount V is at least 0.055 times the length M or more.

By making the carcass line in the area K substantially linear as described above, the carcass is prevented from protruding outward when a load is applied, and the bead portion 2
The amount of deformation itself can be reduced. Further, by forming the substantially linear shape, the thickness of the bead apex rubber 9 is reduced,
The folded-back portion 5B relatively approaches the neutral line of stress, and the compressive force acting on the folded-back portion 5B can be greatly reduced together with the effect of reducing the deformation amount of the bead portion 2 itself. Therefore, in this example, the use of a conventional bead reinforcing member including a cord layer disposed around the bead core 6 and inside and outside the folded portion 5B is excluded.

The deviation amount V is on the convex side, that is, in FIG.
In particular, if it exceeds 0.02M on the positive side, JATMA
When a load more than 3 times the standard load determined by
The contact pressure between the bead portion 2 and the rim flange increases, and the durability of the bead portion 2 is significantly reduced. Further, when the deviation amount V exceeds 0.02M on the concave side, that is, on the negative side, the tension of the carcass cord becomes loose, and the carcass cord is undulated in the buttress portion 15 and the tread crown portion on the tread side portion. It adversely affects the tire profile at the time of filling with standard internal pressure, and reduces uneven wear resistance and the like.

Further, in this example, the bead apex rubber outer end point 9E is radially outward and the main body portion 5A and the folded portion 5 are provided.
A cushion rubber having a thickness T (shown in FIG. 2) of at least 1.6 mm, which is different in rubber hardness from the bead apex rubber 9, is provided between the B and B, which causes bending during tire running. It prevents the ply from peeling due to the shearing force.

In the mounted state X, the carcass line extends in the tread portion 4 in an arc having a radius of curvature R1 centered on the tire equatorial plane and, in the side wall portion 3, the tire maximum. It has a curved profile with a radius of curvature R2 centered on the tire axial direction line Q passing through the width point 16 and a lower radius with a radius of curvature R3 centered on the tire axial direction line Q. Further, the arcuate portion having the radius of curvature R3 and the substantially linear portion in the region K are smoothly joined in the vicinity of the upper adjacent point P1, and the respective radiuses of curvature R1 to R3 are expressed by the following formula (1 ). R1> R2≈R3 (1)

Further, it is desirable that the arcuate portion having the radius of curvature R3 is in contact with the above-mentioned substantially linear portion at the upper adjacent point P1, and this configuration is adopted in this embodiment. This is so configured that the portion radially outside the upper adjacent point P1 is formed as an extended straight line portion of the substantially straight line portion, and the extended straight line portion and the circular arc portion having the radius of curvature R3 are in contact with each other. Then,
This is because, in order to form the extended straight portion, it is necessary to provide a reinforcing layer having high rigidity or to increase the volume of rubber or the like at a portion radially outside the bead apex rubber outer end point 9E. This is not preferable because it causes an increase in the amount of heat generated during driving. Further, if a reinforcing layer having high rigidity is provided and a portion radially outside the bead apex outer end point 9E is formed as the extension straight line portion, the extension straight line portion and the arc portion having the radius of curvature R3 are in contact with each other. In such a case, naturally, the position where the extended straight line portion and the circular arc portion are in contact with each other is substantially the same as the upper end position of the reinforcing layer, and stress tends to concentrate on the position portion during traveling, which causes damage. If the arc portion having the radius of curvature R3 and the substantially linear portion are in contact with each other at the position of the bead apex rubber outer end point 9E as in this example, the contact point is gradually located at the bead apex rubber outer end point 9E. Therefore, the concentration of stress can be suppressed to a minimum, and it is not necessary to dispose extra rubber, resulting in a light weight.

Further, the folded portion 5B of the carcass 5 extends substantially in contact with the outer surface of the bead apex rubber 9, and the carcass line of this contact portion has a concave arc with a radius of curvature R4 centered outside the tire. Curve into a shape. At this time, the radius of curvature R4 <R3. Since the folded-back portion 5B has a concave circular arc shape, it is possible to further ensure that the volume of the bead apex rubber 9 is lowered.
It is possible to prevent ply loosening in B.

The bead apex rubber height H9 from the tire axial line L0 passing through the heel point 13 to the bead apex rubber outer end point 9E is from the tire axial line L0 to the outer surface of the carcass 5 on the tire equator C. Is 0.1 to 0.3 times the carcass height Hk which is the height of the bead apex rubber height H9 is 0.1.
When it is less than Hk, it is difficult to manufacture the tire, and the bead apex rubber 9 is too small, and the carcass 5 in the vicinity thereof is easily bent, and defects such as air pools are likely to occur, and the bent portion becomes a starting point. Induces breaking of the carcass cord during driving. If the bead apex rubber height H9 exceeds 0.3 Hk, the bead apex rubber 9 becomes excessively large, impairing the heat generation property, lowering the durability and increasing the weight. Therefore, more preferably 0.2
It is 5 Hk or less, more preferably 0.20 Hk or less.

The radius of curvature R3 is 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 2 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.

Further, in this example, between the radially inner portion of the sidewall rubber 17 forming the outer surface of the sidewall portion 3 and the folded portion 5B of the carcass 5, side packing rubber extending vertically in the radial direction is provided. The bead portion 2 is provided with chafer rubber 20 that covers the side packing rubber 19 from the bottom surface thereof and that forms the bead base surface 10 and the rising surface 12. The folded-back portion 5 from the tire axial direction line L0
The folding height H5 at the outer end of B, the height H9 of the bead apex rubber, and the chafer height H20 at the outer end of the chafer rubber 20 have the following relationships. H20 <H9 <H5

Further, 10 of the side wall rubber 17
10% to 20 kgf / cm for 0% modulus MS², Side pad
100% modulus MP of locking rubber 19 to 14-4
7 kgf / cm²100% of bead apex rubber 9
Jurassic MA 14-84kgf / cm², Chafer rubber
20 100% modulus MC 55-71kgf / c
m ², 100% modular of carcass 5 topping rubber
37 to 47 kgf / cm²And

In this way, the bead apex rubber 9, side packing rubber 19, and chafer rubber 20 are
Since the rubber whose 100% modulus is within the above range is used, the rigidity of the bead portion 2 can be moderated appropriately, and the deformation of the bead portion 2 can be dispersed in a wide range. As a result, local bending of the bead apex rubber 9 at the outer end in the radial direction can be prevented, the strength of the carcass cord near the outer end can be prevented from being lowered, and the followability with the carcass 5 can be enhanced, so that the separation of the carcass 5 can be improved. , Ply loose, etc. can be prevented.

Since the sidewall rubber 17 has a low 100% modulus MS of 10 to 20 kgf / cm ² , it can be expanded and contracted following the carcass 5, and the chafer rubber 20 has a high modulus to improve the rim displacement resistance. At the same time, separation from the carcass 5 can be prevented, and stress can be prevented from propagating to the bead portion 2.

The 100% modulus MA is 84 kg.
greater than f / cm ² , MP greater than 47 kgf / cm ² , 1
Than 100% modulus MS is 20 kgf / cm ² large, and when 100% modulus MC of greater than 71kgf / cm ^2, the rigidity of the bead portion 2 becomes excessively large, the carcass radially outer end near the bead apex rubber 9 It induces a weakening of the chord, ply loose, etc.

100% modulus MA, MP 14 kg
Smaller than f / cm ² , 100% modulus MS is 10 kgf
/ Cm ² and 100% modulus MC 55 kg
When it is smaller than f / cm ² , the required rigidity of the bead portion 2 cannot be obtained, and the running performance is significantly impaired. The bead apex rubber 9 and the side packing rubber 19 are rubber portions located inside the bead and required to have higher rigidity than the side wall rubber 17. Therefore, the 100% modulus MA is 64 kgf / cm ² or more. The 100% modulus MP is preferably 37 kgf / cm ² or more.

The 100% modulus MT is 10
Since it is set to be larger than 0% modulus MA and MP and smaller than MC, the carcass 5 can be made to follow the deformation of the bead portion 2, and the ply loose or the like can be prevented.

[0051]

[Examples] A heavy-load radial tire having a tire size of 11R22.5 and having the configuration shown in Fig. 1 was prototyped according to the specifications of Tables 1 and 2 (conventional example, Examples 1 to 20, Comparative Examples 1 and 2),
The effect of the present invention was tested. The test conditions are as follows.

1) Heat generation of bead: A test tire was mounted on a standard rim (22.5 × 8.25 at 15 °).
Deep rim), standard internal pressure (8.00 ksc), load (3 times the standard load = 9,000 kg) on a rotating drum tester at a speed of 20 km / h, 5000 km, and 1
The vehicle was run for a distance of 0000 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.

2) Bead Damage Test tires were mounted on a standard rim (22.5 × 8.25 at 15 °).
Deep rim), standard internal pressure (8.00 ksc), load (3 times the standard load = 9,000 kg) on a rotating drum tester at a speed of 20 km / h, 5000 km, and 1
After each of the test tires was run for a distance of 0000 km, each sample tire was disassembled and examined for ply loose. Tables 1 and 2
Among them, ○ indicates that ply loose did not occur, * 1 indicates that loose was generated at the edge of the folded portion of the carcass, and * 2 indicates that the carcass thread was exposed on the bead base surface, Indicates that looseness has occurred, and * 3 indicates that looseness has occurred at the folded portion of the carcass.

3) Rim assembly performance Each sample tire was fitted with a standard rim (22.5 x 8.25 at 15 °).
The workability when assembling the rim to the deep rim) was evaluated based on the feeling of the operator and shown in three stages. In Tables 1 and 2,
3 is good, 2 is slightly bad, and 1 is bad.

4) Tire Weight The weight of each sample tire is shown as an index with the conventional example being 100. A smaller value indicates a lighter weight. The test results are shown in Tables 1 and 2.

[0056]

[Table 1]

[0057]

[Table 2]

As a result of the test, the heat resistance of Examples 1 to 20 is generally lower than that of the conventional example and the comparative example, the durability of the bead portion is improved, and the rim assembly performance is generally good. Moreover, it was confirmed that the tire weight was reduced.

[0059]

INDUSTRIAL APPLICABILITY As described above, the heavy duty radial tire of the present invention can improve the durability of the bead portion while improving the rim assembly performance and the rim displacement resistance performance, and is also useful for reducing the tire weight.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view showing a bead portion in a non-mounted state in which a tire is not mounted on a rim.

FIG. 3 is a graph showing the correlation between the ratio BP / BW and the angle β.

FIG. 4 is a schematic view of a bead portion for explaining a substantially linear state of a carcass line.

[Explanation of symbols]

 2 bead part 3 sidewall part 4 tread part 5 carcass 5A carcass body part 5B carcass folding part 6 bead core 7 belt layer 9 bead apex rubber 9E outer end in the radial direction of bead apex rubber 10 bead base face 11 plane part 12 rising Surface 13 Heel point 15 Straight line J 15 ° Deep rim J1 Rim seat surface J2 Rim flange L Tire axial line LR Radial line X Installed state Y Unmounted state

Claims (5)

[Claims] 1. A carcass provided with a turn-back portion that turns back around the bead core from the inner side to the outer side in the tire axial direction in the main body portion from the tread portion to the bead core of the bead portion, and the inner side of the tread portion. And a radial layer for heavy load, which is mounted on a deep rim of 15 °, and has a belt layer arranged on the outer side in the radial direction of the carcass, wherein the bead core has a shape retention of 0.5 ksc when the tire is mounted on the rim. The inner diameter φBC of the radially innermost end in the mounted state filled with the inner pressure was set to be equal to or less than the inner diameter φBT of the heel point which is the intersection of each extension surface of the bead base surface and the rising surface in contact with the rim flange in the bead portion. Radial tires for heavy loads characterized by the following. 2. When the tire is not mounted on the rim and is not mounted, the bead base surface of the bead portion is angled outwardly and upwardly with respect to the tire axial direction line so that the outside in the tire axial direction is outward in the radial direction. 2. The angle .theta. And the angle .theta. Are 1.0 times or more and 1.9 times or less the angle .alpha. At which the rim seat surface of the rim on which the bead base surface is seated tilts outward and upward. Radial tires for heavy loads. 3. The bead core includes a flat surface portion that is substantially parallel to the rim seat surface at a bottom side facing the rim seat surface in the mounted state, and the tire axial inner end of the flat surface portion and the heel. The length BP in the tire axial direction between the point and the point is 1.3 times or more and 2.1 times or less of the total width BW of the bead core in the direction parallel to the rim sheet surface. Radial tires for heavy loads. 4. The carcass has a lower adjoining point P2 at which the main body of the carcass begins to separate from the bead core, and an intersection P3 at which a radial line passing through the inner end of the plane portion in the tire axial direction intersects with the main body of the carcass. The heavy load radial tire according to claim 3, wherein an angle β formed by the connecting straight line and the tire axial direction line is 45 ° or more and 60 ° or less. 5. The bead portion includes a bead apex rubber that extends in a tapered shape from a bead core toward an outer side in a tire radial direction while passing between a main body portion and a folded portion of the carcass, and the bead portion in the mounted state. The body portion of the carcass has an upper adjacent point P1 in a region K between an upper adjacent point P1 at which the main body portion contacts the radially outer end point of the bead apex rubber and a lower adjacent point P2 that starts to separate from the bead core. A maximum deviation amount V in a direction orthogonal to the straight line N having a length M connecting the lower adjacent point P2 is 0.02 times the length M or less and is substantially linear. The heavy duty radial tire according to claim 1.