JP3180058B2 - Radial tires for heavy loads - 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 radial tire capable of improving the durability of a bead portion.

[0002]

2. Description of the Related Art With the recent improvement of road networks and higher performance of vehicles, high running not only for tires for passenger cars but also for tires for heavy loads used for trucks, buses and the like. Performance is required, and in recent years, a radially structured carcass and a heavy duty radial tire in which the outside of the carcass is fastened with a highly rigid belt layer have been widely used. Such a heavy-load radial tire has high tread rigidity, excellent high-speed performance, and improved wear resistance, low fuel consumption, and the like.

Conventionally, as shown in FIG. 7, for example, a typical bead structure of a heavy-duty radial tire mounted on a rim j having a 5 ° taper rim sheet has a bead core g attached to a carcass main body a. A turn-back portion b that is turned around is provided integrally, and a bead apex c made of hard rubber for reinforcing the bead portion is disposed between the body portion a of the carcass and the turn-back portion b.

[0004] On the other hand, it has been known from experience that a heavy load radial tire is generally liable to damage a bead portion. In particular, there is a lot of damage such as ply loose in which a cord of a folded portion b of a carcass peels off from surrounding rubber. The present inventors have conducted intensive research on such ply loose of the bead portion. As a result, in the conventional tire, the outer surface of the bead portion was in a no-load state in which the rim j was assembled to the rim and filled with the normal internal pressure. It has been determined that the rim flange jf2 is in contact with the flange arc surface jf2 which is continuous with the radially outer end of the rim flange surface jf1 which is the rim width portion and which has an arc angle of about 90 ° and which is curved over a wide range.

In general, during running of a tire, a large repetitive stress acts intensively from the side wall portion to the bead portion in particular, and the bead portion repeatedly deforms to fall down to the rim flange. Has a wide contact area on the flange arc surface jf2, for example, over 70% of the length of the flange arc surface, the deformation amplitude of the tire increases the strain amplitude in the contact area and reaches a very high temperature. Fever. Such a synergistic effect of distortion and heat, which hardens or deteriorates the rubber properties of the bead portion, further generates a crack, and induces loose x at a position such as the outer surface of the folded portion b of the carcass. it is conceivable that.

As described above, an object of the present invention is to provide a heavy-duty radial tire capable of effectively preventing damage to a bead portion, in particular, ply loose, and improving durability. It is another object of the present invention to provide a heavy-duty radial tire capable of improving the durability of a bead portion while reducing the weight of the tire. The invention according to claim 4 further has the above-mentioned object,
It is an object of the present invention to provide a heavy-duty radial tire capable of effectively mitigating shear strain generated between a carcass main body portion and a folded portion and further improving the durability of a bead portion.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a bead portion is folded back around a bead core of a bead portion from a tread portion to a sidewall portion. A carcass comprising a carcass ply in which cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator, and tapered from a bead core to a radially outer side of the bead core between a carcass main body and a folded portion. A heavy load radial tire having a bead apex, wherein in a no-load standard state in which the tire is assembled to a regular rim and filled with a regular internal pressure, an outer surface of the bead portion is formed in a radial direction of a rim flange surface of a rim flange. The outer surface of the bead portion is in contact with the flange arc surface, while being in contact with the flange arc surface which is continuous with the outer end and has a substantially 90 ° arc angle and is curved. And the ratio (St / S) of the contact length St to the arc length S of the flange arc surface is 0.4 to 0.
70.

According to a second aspect of the present invention, the carcass is formed of one carcass ply, and the height H2 of the turn-up portion in the radial direction at the radially outer end of the carcass is set at a maximum from the bead base line BL in the tire radial direction. carcass cross-section that is height to the outer end is Ru 30% to 60% der radial tire for a heavy load height Hc.

According to a third aspect of the present invention, in the tire meridional section in the standard state, the bead portion has the ratio (St / S) of 0.4 to 0.65 and an outer surface of the bead portion. An arc-shaped curved surface portion extending radially outward from an inner point, which is a radially outer point of a contact area in contact with the rim flange, and convex toward the tire lumen side; and In the flange arc surface, the shortest distance between a 60 ° position P of the flange arc surface corresponding to an arc angle of 60 ° from the radially outer end of the rim flange surface and the axial outer surface M of the folded portion of the carcass. When a line segment connected by F intersects with the outer surface of the bead portion at N, the ratio (f) of the length f between MN and the line segment length F
/ F) is 0.4 to 0.9, The radial tire for heavy load according to claim 2, characterized in that:

Further, according to a fourth aspect of the present invention, the carcass folded portion extends radially outward along the axially outer surface of the bead apex and extends from the tire radial outer end of the bead apex to the carcass main body. The heavy-duty radial tire according to any one of claims 1 to 3, further comprising a parallel portion extending parallel to and close to the tire.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an assembly of a tire and a rim in a standard state in which a heavy-load radial tire 1 (hereinafter, simply referred to as a tire 1) is mounted on a regular rim J and filled with a regular internal pressure and has no load. Is shown. As described above, the heavy-duty radial tire according to the present embodiment is mounted on the regular rim.

In the present embodiment, the rim is a 5 ° taper rim having a fixing flange on one side having a rim seat surface Js inclined at 5 ° ± 1 ° with respect to the tire axial direction. As shown in the figure, a radially outer end of a rim flange surface Jf1 forming a rim width portion is provided with a flange circular arc portion Jf2 which is curved with a substantially 90 ° circular arc angle. In this specification, the “regular rim” is a standard rim specified by JATMA, a “Design Rim” specified by TRA, or a rim specified by “Measuring Rim” specified by ETRTO. "Internal pressure" means the maximum air pressure specified by JATMA, and the TRA table "TIRE LOAD LIMITS A
Maximum value described in "T VARIOUS COLD INFLATION PRESSURES" or "INFLATION PRESSUR specified by ETRTO"
E ".

1 and 2, a tire 1 has a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead located at an inner end of each sidewall portion 3. And a body portion 6A extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3 and integrally provided with a fold portion 6B that is folded back from inside to outside in the tire axial direction by the bead core 5. The carcass 6 includes a carcass ply 6a.

The carcass ply 6a is in the form of a sheet in which carcass cords are arranged in an angle range of 70 to 90 ° with respect to the tire equator C, and both sides of which are covered with topping rubber. A steel cord is preferably used as the carcass cord, but if necessary, an organic fiber cord such as nylon, rayon, polyester, or aromatic polyamide can also be used. In the carcass 6 of the present embodiment, the steel cord is
The one formed from a single carcass ply 6a inclined at an angle of about 90 ° with respect to FIG. By configuring the carcass 6 from one carcass ply in this way,
Helps to reduce tire weight.

A belt layer 7 is disposed radially outside the carcass 6 and inside the tread portion 2. Belt layer 7
In this example, the steel cord is attached to the tire equator C,
For example, an innermost belt ply 7A inclined at an angle of about 60 ± 10 ° and a belt ply 7B in which steel cords are arranged at a small angle of 30 ° or less with respect to the tire equator C,
7C and 7D are overlapped, for example, by providing one or more places where the belt cords cross each other between plies.
It has a layered structure. The belt layer 7 can be made of another cord material such as rayon, nylon, aromatic polyamide, and nylon, if necessary.

The bead portion 4 is provided between the body portion 6A of the carcass ply 6a and the folded portion 6B.
The bead apex 8 made of hard rubber is tapered and extends outward in the tire radial direction. The bead apex 8 is, for example, a tire radial height H1 from the bead base line BL, and a carcass sectional height Hc.
6 to 35% (shown in FIG. 1), more preferably 20 to 3%
0%, in this example, about 25% height, for example, JIS
It is desirable to use a hard rubber having an A hardness of 60 to 99 °, more preferably 70 to 95 °.

The "bead base line BL" is defined as a tire axial line passing through the rim diameter position in the standard state, and the "carcass section height" is defined from the bead base line BL in the standard state. The distance in the tire radial direction from the outermost end of the carcass 6 in the tire radial direction is defined.

In the present embodiment, the bead core 5 is formed by rubber-coating a steel wire having a substantially hexagonal cross section by spirally winding a steel wire a predetermined number of times, so that the inner piece 5i extends along the tire axial line. Is configured. Further, since the tire according to the present embodiment is mounted on a 5 ° taper rim, the inner diameter φA of the bead core 5 is equal to the regular rim J.
Is required to be larger than the nominal diameter φB of the rim. If the inner diameter φA of the bead core 5 is smaller than the nominal rim diameter φB of the regular rim J, there arises a problem that the cord of the carcass 6 is exposed on the bead seat surface or the rim cannot be assembled. The bead core 5 may be made of an aromatic polyamide wire material or the like in addition to steel.

The carcass folded portion 6B is located at a height H2 which exceeds the outer end 8t of the bead apex 8 in the radial direction and avoids the tire maximum width position, and has a relatively small amount of distortion when a load is applied. It is preferable that the concentration at the outer end of the folded portion 6B can be reduced by terminating the bent portion 6B. The height H2 is the bead baseline B
It is desirable to set L to 20 to 60%, more preferably 30 to 60% of the carcass sectional height Hc from L, and in this example, it is 4 to 60%.
1%.

Radial outer end height H2 of the folded portion 6B
Is less than 30% of the carcass section height Hc,
Strain tends to concentrate on the outer end of the turned-up portion 6B and separation tends to occur. Conversely, the radially outer end height H2 of the turned-up portion 6B is 60% of the carcass sectional height Hc.
%, It is not preferable because the improvement in durability performance reaches a plateau and rather causes an increase in tire weight.

In the tire meridional section in the standard state, the outer surface of the bead portion 4 is the radially outer end of the rim flange surface Jf1 forming the rim width of the rim flange Jf on the side where the rim seat surface is tapered by 5 °. And the outer surface of the bead portion is in contact with the flange arc surface Jf2, which is curved with an arc angle of approximately 90 °.
The ratio (St / S) of the contact length St contacting with No. 2 to the arc length S of the flange arc surface is 0.2 to 0.70, more preferably 0.4 to 0.65, and still more preferably. 0.5
It is desirable to set it to 0.65.

As described above, the outer surface of the bead portion 4 limits the contact area T (shown in FIG. 2) in contact with the flange arc surface Jf2 to be smaller than the conventional one, so that the bead portion 4 falls into the rim flange Jf generated during tire running. The amplitude of strain and frictional heat generated due to the deformation of the tire can be reduced, and the occurrence of ply loose can be suppressed.

The limited range of the ratio (St / S) was obtained as a result of various experiments by the present inventors. That is, a tire having the structure shown in FIG. 1 in which the ratio (St / S) was variously changed was prototyped to perform a drum durability test, and the temperature inside the bead portion (point A in FIG. 2 ) was measured. 3
As shown in the figure, the ratio (St / S) is 0.4 to 0.70.
, More preferably in the range of 0.4 to 0.65, and still more preferably in the range of 0.50 to 0.65.

In the above ratio (St / S) , contact
On the other hand, if the range of the region T is too small, the amount of bending deformation of the bead portion 4 becomes extremely large, so that frictional heat generation increases, and the effect of preventing looseness cannot be expected. In addition, the ratio (St /
When S) exceeds 0.70, there is not much difference from the conventional tire, and the frictional heat generation or strain amplitude due to the excessively large range of the contact area T increases, and similarly, the effect of preventing looseness cannot be expected.

When the flange arc surface Jf2 has an arc angle of 90 ° or more, a length corresponding to the arc angle of 90 ° is used as the arc length S.

Further, in the present embodiment, the outer surface of the bead portion 4 is formed by a flange arc surface J of the rim flange Jf.
An arc-shaped curved surface portion 9 extending outward from the contact outer point B1, which is a radial outer point of the contact area T in contact with f2, in the tire radial direction and projecting toward the tire lumen side is formed. Such an arcuate curved surface portion 9 helps to reduce heat generation by further reducing the rubber gauge of the bead portion 4 and reducing the internal friction of rubber.

The arcuate curved surface portion 9 is convex toward the tire lumen side, that is, the flange arcuate surface J of the rim flange Jf.
The arc-shaped curved surface portion 9 and the rim flange J are formed when the bead portion 4 falls down to the rim flange side during running of the tire and is deformed.
Since the friction of f with the flange arc surface Jf2 is extremely reduced, the heat generation or distortion of the bead portion 4 can be further reduced, and the generation of looseness can be suppressed.

In this embodiment, the arc-shaped curved surface portion 9
Exemplifies that which is smoothly connected to the outer surface arc of the sidewall portion 4, but as shown by a dotted line in FIG. 2, the arc-shaped curved surface portion 9 has a curvature radius R1 having a center on the tire lumen side.
May be formed so as to intersect with the outer surface arc C1 of the side wall portion 4 so that the intersection portion thereof appears as a ridge line in the tire circumferential direction. When the arcuate curved surface portion 9 is formed in this manner, the radially outer end B2 is, as shown in FIG. 2, separated from the bead base line BL by the carcass sectional height Hc.
15% to 35%, more preferably 20% to 30%, even more preferably 22% to 28%, and in this example, the height H of 25%
3, which is set to be substantially equal to the height H1 of the bead apex 8.

In the above case, if the radially outer end height H3 of the arcuate curved surface portion 9 is less than 15% of the carcass sectional height Hc, it becomes difficult to reduce the rubber gauge of the bead portion 4 and the arcuate curved surface portion 9 and flange arc surface Jf of rim flange Jf
There is a tendency that the effect of reducing the friction with No. 2 tends to decrease, and if it exceeds 30%, the rigidity of the bead portion 4 tends to decrease. Note that, as in this example, the outer end B2 of the arc-shaped curved surface portion 9
To the outer end 8t of the bead apex 8 made of hard rubber.
It is preferable that the bead portion is located at a position equal to or more than the above, since the rigidity of the bead portion can be prevented from lowering.

In the meridional section of the tire, the arc-shaped curved surface portion 9 is preferably formed by a single or a plurality of arcs. When a single arc is used, the radius of curvature is set to the carcass cross-sectional height Hc. It is preferably set to 20 to 30%.

In this embodiment, as shown in FIG. 4, the flange arc surface Jf2 has a 60 ° position P on the flange arc surface Jf2 corresponding to an arc angle of 60 ° from the radially outer end of the rim flange surface Jf1. And a line segment connecting the carcass folded portion 6B with the axially outer surface M at the shortest length F, where N is an intersection point intersecting the outer surface of the bead portion; The ratio to the line segment length F (f /
An example is shown in which the rubber gauge is determined so that F) is 0.4 to 0.9.

As a result of the experiment by the present inventors, the looseness of the bead portion 4 is located at the 60 ° position of the flange arc surface corresponding to the arc angle of 60 ° from the radially outer end of the rim flange surface Jf1 in the flange arc surface Jf2. P and a line connecting the axially outer surface M of the folded portion 6B of the carcass with the shortest length F is generated around the point M, which is the center of the line segment. Rubber gauge, ie the MN
It has been found that by regulating the length f between the beads, the heat generation of the bead portion 4 can be controlled to prevent loosening.

That is, a tire having the structure shown in FIG. 1 in which the ratio (f / F) was variously changed was prototyped, and a drum durability test was performed. The temperature around the point M was measured.
As shown in the above, when the ratio (f / F) exceeds 0.9,
The stiffness of the bead 4 can be increased, but the rim flange Jf
If the ratio (f / F) is less than 0.4, the rubber gauge of the bead portion is insufficient, the rigidity is reduced, the steering stability is reduced, and the structural destruction is reduced. Can happen. From this viewpoint, the ratio (f / F) is preferably set to 0.4 to 0.6.

Further, in the present embodiment, as shown in FIG. 4, the folded portion 6B of the carcass extends radially outward in the form of an inward bulge once along the outer side surface 8o of the bead apex 8 and the bead. From the position of the outer end 8t of the apex 8, a parallel portion G extending substantially parallel to the carcass main portion 6A and extending substantially in parallel is terminated.

As described above, by providing the parallel portion G extending in the tire radial direction in the vicinity of the main body 6A of the carcass 6, the shear strain between the carcass cord of the main body 6A and the folded portion 6B is reduced and the folded portion is formed. Since a sufficient space in the thickness direction for disposing the clinch rubber 13, the side rubber 14, and the like can be provided on the outer surface of the portion 6B, and the carcass folded portion 6B can be kept away from the outer surface of the bead portion 4, the bead This is preferable in that heat due to friction between the outer surface of the portion 4 and the rim flange Jf is hardly transmitted, and the effect of preventing the generation of looseness can be further enhanced.

The length L of the parallel portion G is, for example, 2.0 to 8.0 times the maximum cross-sectional width CW of the bead core 5 (measured for the wire portion) in the standard state,
More preferably, it is desirably 3.5 to 6.5 times, and still more desirably, 4.0 to 6.0 times. In the present embodiment, the parallel portion G is about 5.0 times the maximum cross-sectional width CW of the bead core.
And double.

If the length L of the parallel portion G is less than 2.0 times the maximum cross-sectional width CW of the bead core, the main body 6A
The effect of alleviating the shearing force between the carcass cords of the carcass cord and the folded portion 6B is likely to be insufficient. Conversely, if it exceeds 8.0 times, the outer end in the tire radial direction of the carcass folded portion 6B is located at the tire maximum width position where the bending is severe. It has been confirmed from the results of various experiments that the bead durability tends to decrease due to the tendency to loosen due to the close proximity to.

As shown in FIG. 6, which is a cross-section taken along the line AA in FIG. 4, the carcass main body 6A and the folded back portion 6B are close to each other at the parallel portion G as an example.
And the distance Q between the carcass cords of the folded portion 6B is maintained at, for example, 1.0 to 4.5 times, preferably 1.5 to 3.5 times the diameter D of the carcass cord 11, and the carcass main body 6A It is desirable that the shearing force acting between the carcass cords of the folded portion 6B be reduced by the elasticity of the rubber material interposed between the carcass cords.

When the inter-cord distance Q is less than 1.0 times the diameter D of the carcass cord, the carcass cord 11
They tend to come close to each other, and the effect of reducing the shearing force by the rubber between the cords becomes insufficient, and the carcass cords 11 may partially come into contact with each other, which may cause cord looseness. Further, when the inter-cord distance Q exceeds 4.5 times the diameter D of the carcass cord, the folded portion 6B
Becomes closer to the outer surface of the bead portion and becomes more susceptible to the heat generated on the outer surface of the bead portion.

The rubber material interposed between the carcass cords 11 of the carcass body 6A and the folded portion 6B may use the topping rubber of the carcass ply 6a. The figure shows a cushion rubber layer 12 interposed separately between 6A and the folded portion 6B. And the cushion rubber layer 12
The cushion rubber layer 12 having a hardness substantially equal to that of the topping rubber, a hard rubber harder than the topping rubber, and the like for reinforcing the bead portion 4 can be separately employed.

As shown in FIGS. 2 and 4, the radial tire for heavy load according to the present embodiment has a bead portion 4 in which a clinch rubber 13 is disposed in a bead portion which comes into contact with a rim. are doing. This clinch rubber 13
Has a JISA hardness of 60 to 90 °, more preferably 65 °
By using a hard rubber of up to 85 °, rim misalignment, wear due to contact with the rim, and the like can be prevented.

A flexible side rubber 14 is disposed radially outside the clinch rubber 13. further,
The radial tire for heavy load 1 of the present example exemplifies a tire in which a bead portion 4 is not provided with a cord reinforcing layer made of a cord ply in which an organic fiber cord or a steel cord is arranged separately from the carcass ply 6a. This helps to reduce tire weight.

[0043]

EXAMPLE A heavy-duty radial tire having a tire size of 10.00R20 was prototyped based on the specifications shown in Table 1 (Examples 1 to 5, Comparative Examples 1 and 2, Conventional Example), and a durability test of a bead portion was performed. Was. The common specifications of the tires are as follows. <Carcass>-Number of plies: 1-Cord configuration Steel cord (3 x 0.20 + 7 x 0.23)-Cord angle 90 degrees to tire equator-Cord density: 38 / 5cm <Belt layer>-Number of plies: 4 -Cord configuration Steel cord (3 x 0.20 + 6 x 0.35)-Cord angle + 67 / + 18 / -18 / -18 degrees from the inner ply to the tire equator-Cord density 26 wires / 5cm It is as follows.

<Durability of Bead Section>
Mounted on a regular rim of 0x20, filled with an internal pressure of 1000 kPa, run on a drum at a load of 9000 kgf and a speed of 20 km / h. When the damage that can be visually confirmed was generated, the running was terminated and damage occurred. Distance L1 and finish distance L0
(10000 km), the ratio L1 / L0 is 10
It was evaluated by an index of 0. The higher the value, the better.

<Tire Weight> The weight per tire was measured and expressed as an index with the conventional example being 100. The smaller the value, the smaller the tire weight. Table 1 shows the test results.

[0046]

[Table 1]

As a result of the test, it was confirmed that in the tire of the example, the durability of the bead portion was improved. Note that substantially the same measurement results are obtained for other tire sizes.

[0048]

As described above, according to the first and second aspects of the present invention, the outer surface of the bead portion in the meridional section of the tire in a no-load state in which the tire is assembled to the normal rim and filled with the normal internal pressure, By limiting the range of the contact area that comes into contact with the flange arc surface, the amplitude of strain and frictional heat generated due to the deformation of the tire that falls into the rim flange generated while the tire is running can be reduced, and the ply loose such as the folded part of the carcass can be reduced. It can be suppressed effectively.

According to the third aspect of the present invention, the outer surface of the bead portion extends radially outward from the contact outer point, which is a radially outer point of the contact area in contact with the rim flange, toward the tire cavity side. By forming a convex arcuate curved surface part, the rubber gauge of the bead part is further reduced, heat generation and tire weight are reduced, while running the tire,
When the bead portion falls down toward the rim flange side, the friction between the arcuate curved surface portion and the flange arc surface of the rim flange becomes extremely small, so that the heat generation of the bead portion can be further reduced and the looseness can be suppressed.

Further, according to the third aspect of the present invention, in the flange arc surface, 60 ° from the radial outer end of the rim flange surface.
60 ° position P of the flange arc surface corresponding to the arc angle of
When a line segment connecting the carcass folded portion with the axially outer surface M at the shortest length F is an intersection point intersecting the bead portion outer surface at N, the length f between the MNs and the line segment length By setting the rubber gauge so that the ratio (f / F) to the height F is 0.4 to 0.9, the heat generation of the bead portion can be suppressed low, and the generation of the looseness can be further prevented.

According to the fourth aspect of the present invention, the folded portion of the carcass extends along the outer surface of the bead apex and is substantially parallel to the main body of the carcass from a position substantially at the outer end of the bead apex. By forming a parallel portion that extends, it is possible to provide a sufficient space in the thickness direction for arranging rubber on the outer surface of the folded portion, and it is possible to keep the folded portion of the carcass away from the outer surface of the bead portion, The effect of preventing heat from being transmitted due to friction between the outer surface of the bead portion and the rim flange can be further enhanced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view (right half) of a tire according to an embodiment of the present invention.
It is.

FIG. 2 is an enlarged sectional view of a bead portion.

FIG. 3 is a graph showing a relationship between a temperature of a bead portion and a ratio (St / S).

FIG. 4 is an enlarged sectional view of a bead portion.

FIG. 5 is a graph showing a relationship between a temperature of a bead portion and a ratio (f / F).

FIG. 6 is a sectional view taken along line AA of FIG. 3;

FIG. 7 is an enlarged sectional view of a bead portion of a conventional heavy duty radial tire.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6a Carcass ply 6A Carcass ply main body 6B Carcass ply folded back part 8 Bead apex J Regular rim Jf Rim flange Jf1 Rim flange surface Jf2 Flange arc surface

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 15/00-15/024

Claims (4)

(57) [Claims] 1. A carcass ply in which a bead is folded back around a bead core of a bead portion from a tread portion to a sidewall portion and locked, and cords are arranged at an angle of 70 to 90 ° with respect to the tire equator. A heavy duty radial tire having a carcass and a bead apex extending radially outward from the bead core in the tire radial direction between the carcass main body portion and the folded portion, wherein the tire is rim-assembled into a regular rim and a regular internal pressure is applied. In the no-load standard state filled with rim, the outer surface of the bead portion is connected to the radially outer end of the rim flange surface of the rim flange to form approximately 9
A ratio of a contact length St at which the outer surface of the bead portion comes into contact with the flange arc surface and an arc length S of the flange arc surface while contacting the flange arc surface curved with an arc angle of 0 ° ( S
(t / S) is 0.4 to 0.70. 2. The carcass is composed of one carcass ply, and a height H2 of a radially outer end of the folded portion is:
The carcass sectional height Hc, which is the height from the bead base line BL to the outermost end in the tire radial direction of the carcass, is 3
Ru 0-60% der 請 Motomeko 1 heavy duty radial tire according. 3. In the tire meridional section in the standard state,
The bead portion sets the ratio (St / S) to 0.4 to 0.6.
5, and an outer surface of the bead portion is formed in an arc shape in which the outer surface of the bead portion extends radially outward from the contact outer point, which is the radial outer point of the contact area in contact with the rim flange, and is convex toward the tire bore. A 60 ° position P of the flange arc surface corresponding to an arc angle of 60 ° from a radially outer end of the rim flange surface, wherein the flange arc surface of the rim flange has a curved surface portion; Assuming that a line segment connecting the outer surface M in the direction with the shortest length F is an intersection point intersecting with the outer surface of the bead portion, N, a ratio of the length f between MN and the line segment length F ( f /
3. The method according to claim 2, wherein F) is 0.4 to 0.9.
The radial tire for heavy load described. 4. The folded portion of the carcass extends radially outward along the axially outer surface of the bead apex, and extends in parallel from the tire radial outer end of the bead apex in close proximity to the carcass body. The heavy-duty radial tire according to any one of claims 1 to 3, further comprising a parallel portion.