JP3180059B2 - 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. 12, for example, a typical bead structure of a heavy-duty radial tire in which a rim sheet j1 is mounted on a rim j having a taper of 5 ° is a bead core g attached to a carcass main body a. And a bead apex c made of hard rubber for reinforcing a bead portion is disposed between the body portion a and the folded portion b of the carcass. A chafer rubber d made of rubber having a large modulus is arranged on the outer surface of the folded 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 a bead portion.When topping a carcass cord, a rubber having a modulus smaller than that of the chafer rubber is usually used. It has been found that a large difference in modulus occurs on the outer surface of the portion b, and distortion due to the bending deformation of the carcass is likely to concentrate on this portion, causing separation, ply loose and the like.

[0005] The invention according to claims 1 to 3 of the present invention,
A folded portion of the carcass is provided with a parallel portion extending in parallel from the tire radial outer end of the bead apex to the carcass body portion, and a side packing rubber having a specific modulus is arranged on the tire axial outside surface of the folded portion. It is an object of the present invention to provide a heavy-duty radial tire capable of effectively preventing damage to a bead portion, in particular, ply loose traveling from inside the tire, and improving durability.

Further, in addition to the above object, the invention according to claim 4 suppresses a crack which tends to occur on the tire outer surface from the sidewall portion to the bead portion for a long time,
It is an object of the present invention to provide a heavy-duty radial tire capable of improving the durability of a bead portion by effectively preventing ply loose traveling from outside the tire.

[0007] In addition to the above objects, the invention according to claims 5 and 6 further provides a tire meridional section in a no-load state in which the tire is assembled to a regular rim and filled with a regular internal pressure.
Based on limiting the area where the outer surface of the bead portion comes into contact with the flange arc surface, the amplitude of strain and the frictional heat generated due to the deformation of the tire falling into the rim flange generated during tire running can be reduced, and the carcass turn-back part etc. It is an object of the present invention to provide a heavy duty radial tire that can effectively suppress the ply looseness and further improve the durability of the bead portion.

[0008]

According to a first aspect of the present invention, a bead core is folded from a tread portion to a bead core of a bead portion through a tread portion to a bead portion from the inner side to the outer side in the tire axial direction. Between the carcass consisting of a carcass ply in which a folded portion extending radially outward and extending at an angle of 70 to 90 ° with respect to the tire equator is arranged, and between the carcass body and the folded portion. A heavy load radial tire having a bead apex extending in a tapered shape from the bead core outward in the tire radial direction, wherein the folded portion extends radially outward along the axially outer surface of the bead apex and has a bead apex. A parallel portion extending in parallel to and proximate to the main body of the carcass from the tire radial outer end,
A 100% modulus Mp of 47 to 65 kgf / cm ² is provided on the outer side of the folded portion in the tire axial direction, and a carcass cord topping is provided.
100% modulus Mt of rubber and side packing
10kgf the difference between the 100% modulus Mp of the arm / cm ² or more
A radial tire for heavy loads, characterized in that:

[0009] According to a second aspect of the invention, the bead portion,
100 that covers the outer surface of the side packing rubber in the tire axial direction and is exposed on the outer surface of the bead portion and the bead seat surface.
A chafer rubber having a% modulus Mc of 55 to 75 kgf / cm ² is provided, and the chafer rubber has an outer surface of a sidewall portion and a 100% modulus Ms of 10 to 75 kgf / cm ^2.
A side wall rubber of 20 kgf / cm ² is connected, and the length of the parallel portion G is adjusted to the cross section of the bead core.
It is characterized by being 2.0 to 8.0 times the width CW.
You .

[0010] The invention of claim 3, wherein the radial outer end height of the folded portion H2 is 30 to the carcass section height Hc
It is characterized by being 60% .

According to a fourth aspect of the present invention, the tire is
Assemble to rim and 0.5kgf / cm ^TwoFilled the internal pressure of
Expansion change from temporary assembly state to standard state filled with normal internal pressure
The outermost tie in the tire axial direction.
The maximum width point P1 and half of the contact area where it contacts the rim flange.
Surface of the area between the contact outer point P2 which is the radial outer point
Has a maximum principal strain εm of 4% or less, and a maximum principal strain of the region described above.
Difference between εm and the maximum principal strain εp at the tire maximum width point P1
(Εm−εp) is less than 2%
Item 1. The radial tie for heavy load according to any one of Items 1 to 3.
Ya.

In a fifth aspect of the present invention, when the tire is rim-assembled on a regular rim and a normal internal pressure is applied and no load is applied, the bead seat surface of the bead portion has an interference between the bead portion and the rim seat surface. An outer surface of the bead portion is connected to a radially outer end of the rim flange surface of the rim flange and contacts a flange arc surface curved with an arc angle of about 90 °, and the outer surface of the bead portion has a flange. The ratio (St / S) of the contact length St in contact with the arc surface to the arc length S of the flange arc surface is 0.2 to 0.70.
The heavy load radial tire according to any one of claims 1 to 4, wherein:

According to a sixth aspect of the present invention, in the tire meridional section in the above state, the bead portion has an interference between a bead seat surface and a rim seat surface and the ratio (St / S) is set to 0. .2 to 0.65, and the outer surface of the bead portion extends outward from the contact outer point P2, which is the radial outer point of the contact area in contact with the rim flange, in the tire radial direction and toward the tire lumen side. 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 in the flange arc surface, and a turn-back portion of the carcass. A line segment connecting the outermost surface in the shortest length F to
Assuming that the intersection point intersecting with the bead portion outer surface is N, the ratio (f / F) of the length f between the PNs to the line segment length F is 0.4.
The heavy-duty radial tire according to claim 5, wherein the diameter is from 0.9 to 0.9.

[0014]

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, and this fixing flange is shown in FIG. 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. For example, the carcass 6 includes one carcass ply 6a. By configuring the carcass 6 from one carcass ply in this way, it is useful to reduce the weight of the tire.

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
An example is shown that is inclined at an angle of about 90 ° with respect to. In the present embodiment, the carcass cord having a 100% modulus Mt of 37 to 47 kgf / cm ² is exemplified.

A belt layer 7 is disposed radially outside the carcass 6 and inside the tread portion 2. In the present embodiment, the belt layer 7 includes the innermost belt ply 7A in which the steel cord is inclined at an angle of, for example, about 60 ± 10 ° with respect to the tire equator C, and the steel cord whose tire cord is 30 ° or less with respect to the tire equator C. Belt plies 7 inclined at a small angle
B, 7C, and 7D have a four-layer structure in which, for example, one or more locations where the belt cords cross each other between plies are provided and overlapped. 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, as shown in FIG. 1, the height H1 in the tire radial direction from the bead base line BL is 6 to 35% of the carcass sectional height Hc, more preferably 8 to 25%.
%, More preferably 15 to 25%,
In this example, the height is set to about 21%.

The "bead base line BL" is defined as a line in the tire axial direction passing through the rim diameter position in the standard state, and the "carcass sectional height" is defined as the carcass sectional height from the bead base line BL in the standard state. No. 6 is defined as the distance in the tire radial direction to the outermost end in the tire radial direction.

The bead apex 8 is shown in FIG.
As described above, in this example, the outer surface 8o in the tire axial direction is
It is formed in the shape of an inwardly bulging arc depressed inward in the direction.
If 100% modulus Ma is 14-84 kgf / cm^Two, Good
Preferably 55 to 84 kgf / cm ^Two, More preferably 64-
84kgf / cm^TwoIt is desirable to form with rubber.

100% of the bead apex 8
When the modulus Ma exceeds 84 kgf / cm ² ,
The rigidity of the bead portion 4 becomes excessive, and the bead apex 8
In the vicinity of the outer end in the radial direction, the carcass cord is easily bent locally, and tends to induce a decrease in strength, ply loose and the like. 100% modulus M of Bead Apex 8
When a is smaller than 55 kgf / cm ² , necessary bead portion 4
Stiffness cannot be obtained, and the steering stability tends to be greatly reduced.

In this embodiment, the bead core 5 is formed by spirally winding a steel wire a predetermined number of times to form a substantially hexagonal cross section and coating the rubber with a rubber, and the inner piece 5i is along the tire axial direction. 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.
Must 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 radially outward 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 turning height H2 of the carcass is from 20 to the carcass sectional height Hc from the bead base line BL.
60%, preferably 30-60%, more preferably 35%
It is desirable to set it to about 45%, and in this example, it is set to about 41%. When the radially outer end height H2 of the folded portion 6B is less than 30% of the carcass sectional height Hc, strain tends to concentrate on the outer end of the folded portion 6B and separation tends to occur. Conversely, even if the radially outer end height H2 of the folded portion 6B exceeds 60% of the carcass cross-sectional height Hc, the improvement of the durability performance reaches a peak and the tire weight is rather increased, which is not preferable.

In the present embodiment, the folded portion 6B of the carcass is formed with the outer surface 8 of the bead apex rubber 8.
Along the line o, a parallel portion G is formed which once extends inward in the radial direction and extends substantially in parallel with the carcass body portion 6A from the position of the substantially outer end 8t of the bead apex rubber 8. And is terminated.

[0027] And the radially inner edge in the tire axial direction outer side of the turnup portion 6B of the carcass, the 100% modulus Mp forming the outer end tapering is 47 ~65kgf / cm ^2,
More preferably, a side packing rubber 9 of 47-60 kgf / cm ² is arranged, and its radially outer end 9t is located outside the outer end 8t of the bead apex 8 and, in this example, inside the outer end of the parallel portion G. Is terminated.

By arranging the side packing rubber 9 having a smaller modulus than that of chafer rubber or the like on the outer surface of the folded portion 6B of the carcass, the difference in modulus of the interface between the carcass 6 and the topping rubber can be reduced. By relaxing the concentration of strain, looseness of the folded portion 6B can be prevented and bead durability can be improved.

When the 100% modulus Mp of the side packing rubber 9 is less than 14 kgf / cm ² , the followability to the carcass is improved, but the rigidity of the bead portion is reduced, and the steering stability is greatly reduced. Conversely, if it exceeds 65 kgf / cm ² , the modulus difference between the carcass and the topping rubber tends to increase, and the effect of preventing ply loose decreases.
More preferably, the topping rubber of carcass cord is 10
0% modulus Mt and 100 of side packing rubber
It is desirable that the difference from the% modulus Mp be 10 kgf / cm ² or less, more preferably 5 kgf / cm ² or less.

The outer end 9t of the side packing rubber 9
However, if it is located inside the outer end 8t of the bead apex 8, the effect of relaxing the distortion following the carcass 6 that is relatively greatly bent at the outer end 8t of the bead apex 8 during tire running is obtained. Will drop. If the outer end 9t of the side packing rubber 9 extends outside so as to wrap the outer end of the parallel portion G, it is preferable to prevent looseness of the folded portion 6B, and particularly to prevent a cord loose at the outer end of the folded portion 6B. It is preferable in that it can be prevented. In addition, the side packing rubber 9 includes an inner end 9b and an outer end 9 in the tire radial direction.
It is also preferable that t has a tapered shape so that a rigidity step generated with other peripheral rubbers can be reduced as much as possible and dispersion of strain can be achieved.

In the present embodiment, as shown in FIG. 2, the radially inner end 9b of the side packing rubber 9 is
Are located on an axial line extending outward in the axial direction from the approximate center. Then, in order to effectively prevent the ply loose and the like of the folded portion 6B of the carcass,
The height H3 of the inner end 9b is equal to the carcass sectional height Hc.
Is preferably set to 1 to 8%, and in this example, it is set to 4.5%. The outer end height H4 of the side packing rubber 9
Is preferably 25% to 65% of the carcass sectional height Hc, and is 31% in this example.

As described above, in this embodiment, the height H1 of the bead apex, the turning height H2 of the carcass, and the outer end heights H3 and H4 of the side packing rubber satisfy H3 <H1 <H4 <H2. Although the setting is made so as to satisfy the relationship, H3 <H1 <H2 <H4 may be satisfied.

The maximum thickness t (shown in FIG. 2) of the side packing rubber 9 is the maximum cross-sectional width C of the bead core 5.
It is most effective to set W to 0.2 to 0.7 times.
If the thickness t is less than 0.2 times the maximum cross-sectional width CW of the bead core 5 (for the wire portion), the effect of the side packing rubber 9 to prevent the looseness of the folded portion 6B of the carcass from being relatively reduced. On the contrary, when the thickness t is
If the cross-sectional maximum width CW of the bead core 5 exceeds 0.7 times, the rubber gauge of the bead portion 4 tends to increase, and the heat generation of the bead portion 4 tends to increase.

In the present embodiment, the bead portion 4 is provided with a chafer rubber 10 which covers the entire outer surface of the side packing rubber 9 in the tire axial direction and is exposed on the outer surface 4a of the bead portion 4 and the bead seat surface 4b. I have.
The chafer rubber 10 has a 100% modulus Mc of 55 to 75 kgf / cm ² , more preferably 60 to 75 kgf / cm ² .
/ Cm ² is desirable. The chafer rubber 10 having such a large modulus suitably increases the rigidity of the outer surface 4a of the bead portion 4 and the bead seat surface 4b which come into contact with the rim J, and effectively suppresses rim misalignment or damage due to contact with the rim. It is preferable in that it is possible.

[0035] In the 100% modulus Mc is less than 55 kgf / cm ² of the chafer rubber 10 tend not otherwise be sold sufficient rigidity to withstand contact with the rim, when a reverse in excess of 75 kgf / cm ^2, the bead Excessively increase the rigidity of the part. In this example, the chafer rubber 1
In FIG. ^2, a side wall rubber 14 having an outer surface of the side wall portion 3 and having a 100% modulus Ms of 10 to 20 kgf / cm ² is connected.

By providing the side packing rubber 9 and restricting the 100% modulus of the carcass topping rubber, chafer rubber and the like, the rigidity of the bead portion 4 is moderately reduced while the bead portion 4 is deformed. Strain can be dispersed over a wide range. Further, the side packing rubber 9 is provided at the outer end 8 of the bead apex 8.
At this time, the local bending of the carcass 6 at t can be prevented, the strength of the carcass cord near the outer end 8t can be prevented from decreasing, and the difference in modulus from the topping rubber can be reduced by regulating the rubber modulus. In addition, the ability to follow the carcass 6 can be enhanced, and separation, ply loose and the like of the carcass 6 can be effectively prevented. Further, the 100% modulus Ms of the sidewall rubber 14 is set to 10 to 20 kgf.
/ Cm ² , it is possible to expand and contract flexibly following the bending deformation of the carcass 6 in the sidewall portion 3 that can be deformed most greatly.

Further, by forming the parallel portion G in the carcass body portion 6A and the folded portion 6B,
Tire 1 is assembled to the regular rim J and 0.5kgf / cm
^{When the} inflation is changed from the temporary assembly state filled with the internal pressure to the standard state filled with the normal internal pressure as shown in FIG. 1, the tire maximum width point P1 which is the outermost in the tire axial direction as shown in FIG.
Maximum principal strain ε on the surface of the region Y between the contact point P2 which is the radially outward point of the contact area in contact with the flange of the rim.
m is set to 4% or less, and the difference (εm) between the maximum principal strain εm in the region Y and the maximum principal strain εp at the tire maximum width point P1.
−εp) can be regulated to less than 2%.

In general, in a heavy-duty radial tire, extremely large repetitive stress generated during running acts intensively from the sidewall portion 3 to the bead portion 4 and the action of ozone in the air causes minute repetitive stress in these regions. Cracks, which are cracks, may occur, and the cracks on the outer surface of the tire may cause the bead portion to bend and deform due to bending deformation of the bead portion, which may cause the above-mentioned ply loose. According to the study of the present inventors, it has been found that such cracks are closely related to the maximum principal strain on the tire surface, and in the expansion change, the maximum principal strain εm and the maximum principal strain on the surface of the region Y are determined. It has been found that regulating the difference (εm−εp) between the maximum principal strain εm and the maximum principal strain εp at the tire maximum width point P1 is effective for preventing cracks.

Here, the length L of the parallel portion G has a close effect on the maximum principal strain in the region Y. The length L can be determined by a balance between the carcass turning height H2 and the outer end height H1 of the bead apex. Preferably, the length L of the parallel portion G is the maximum cross section of the bead core 5 in the standard state. 2.0 to 8.0 times the width CW, more preferably 3.5 to 6.5 times, and still more preferably 4.0 to 8.0 times the width CW.
It is desirable to set it to be 6.0 times, and in the present embodiment, it is formed about 5.0 times.

When the length L of the parallel portion G is smaller than 2.0 times the maximum width CW of the cross section of the bead core, a peak of the maximum principal strain εm easily appears in the region Y. Cracks tend to occur relatively early and concentrated at the peak position of the main strain εm, and conversely, if it exceeds 8.0 times, the outer end in the tire radial direction of the folded portion 6B of the carcass becomes the tire maximum width point at which the bending is severe. It has been confirmed from the results of various experiments that it is easy to approach P1 and the bead durability tends to decrease.

As shown in FIG. 3, which is a cross section taken along line AA of FIG. 2, as an example in which the carcass main body 6A and the folded portion 6B are close to each other at the parallel portion G, the carcass main body 6A
And the distance Q between the carcass cords 11 and 11 of the turn-back portion 6B
For example, the diameter D of the carcass cord 11 is 1.0 to 4.
5 times, preferably 1.5 to 3.5 times, and the shear force acting between the carcass cords of the carcass main body 6A and the folded portion 6B is increased by the elasticity of the rubber material interposed between the carcass cords. It is desirable to relax.

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 effect of reducing the maximum principal strain ε on the surface of the region Y even when the main body 6A and the folded portion 6B extend in parallel. Tends to decrease,
In addition, the thickness of the bead portion 4 is unnecessarily increased.

In this embodiment, the carcass body 6A
The rubber material interposed between the carcass cords of the folded portion 6B utilizes the topping rubber 12 of the carcass ply 6a, and the carcass ply body portion 6A and the folded portion 6B are used.
A cushion rubber layer having a modulus substantially equal to that of the topping rubber 12 or a modulus larger than that of the topping rubber 12 may be separately provided.

FIG. 4 shows the measurement results of the maximum principal strain εm of the conventional tire and the tire of the present invention. As is clear from FIG. 4, in the conventional tire, the maximum principal strain εm has a peak Z of 7 to 8% in the region Y and decreases to about 2% at the tire outermost point P1 in the expansion change. I have. That is, the maximum principal strain εm is large, and the maximum principal strain εm in the region Y and the maximum principal strain ε at the tire maximum width point P1 are obtained.
The differential relative strain with respect to p (εp−εm) is as large as 5% or more.

On the other hand, in the tire of the present invention, the area Y
Is less than or equal to 4%, and the maximum principal strain εm in the region and the maximum principal strain εp at the tire maximum width point P1.
Is controlled to be less than 2% as a result, there is substantially no peak of the maximum principal strain εm, and the relative strain in this region Y is also reduced.

As a result, in the radial tire for heavy load according to the present embodiment, the maximum principal strain on the tire surface can be made extremely small in the region Y from the sidewall portion 3 to the bead portion 4, so that the deformation and the atmospheric As a result of effectively suppressing cracks caused by the influence of ozone over a long period of time, it is possible to prevent the looseness from traveling from the outer surface of the bead portion 4 to the inside of the tire. Therefore, the bead portion 4 is further combined with the effect of preventing the looseness from advancing from the inside of the bead portion 4 by the side packing rubber 9.
Can be improved in durability.

If the maximum principal strain εm exceeds 4%, the rubber deteriorates due to repeated deformation of the side wall portion due to running, and furthermore, due to the influence of ozone in the atmosphere, etc.
It is not preferable because cracks tend to be concentrated on portions having high distortion. The difference (εp−) between the maximum principal strain εm in the region Y and the maximum principal strain εp at the tire maximum width point P1.
If there is a portion where [epsilon] m exceeds 2%, the relative strain with respect to the tire maximum width point P1 increases, and cracks tend to concentrate at such a position.

The measurement of the maximum principal strain εm is performed as follows, as shown in FIG. The surface of the sidewall portion 3 and the bead portion 4 of the sample tire are buffed and wiped off with naphtha, an adhesive is applied to the polished surface, and a measurement reference line RL extending in the tire radial direction is drawn. Using a white ink (titanium oxide + DOP + castor oil), copy a plurality of circles of markings as shown in FIG. 5 onto a vinyl tape 15. Assemble the vinyl tape 15 into a rim and add 0.5 kgf / cm.
Affix and transfer along the measurement reference line to the polished surface of the test tire filled with the internal pressure of ² , and further, after filling the air pressure to the normal internal pressure, the mark on the sidewall portion of the tire is replaced with a new tape. Copy to the mark thus obtained (0.5 kgf / cm
² reference conditions at the time the inner pressure filling, to expand the comparison condition) during normal internal pressure, several measures the gauge shown in FIG. 6 1-11
The maximum principal distortion is calculated using the equation shown by.

[0049]

(Equation 1)

[0050]

(Equation 2)

[0051]

(Equation 3)

[0052]

(Equation 4)

[0053]

(Equation 5)

[0054]

(Equation 6)

[0055]

(Equation 7)

[0056]

(Equation 8)

[0057]

(Equation 9)

[0058]

(Equation 10)

[0059]

[Equation 11]

In this embodiment, as shown in FIG.
In the tire meridional section in the standard state, the outer surface of the bead portion 4 has a rim flange Jf on the rim seat side having a 5 ° taper.
The outer surface of the bead portion comes into contact with the flange arc surface Jf2 while being 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 is curved with an arc angle of about 90 °. The ratio (St / S) of the contact length St of the flange to the arc length S of the flange arc surface is 0.
2 to 0.70 are illustrated.

In the conventional heavy duty tire mounted on the 5 ° taper rim, the outer surface 4a of the bead portion 4 was in wide contact with the flange arc surface jf2 in the standard state. Therefore, the bead portion 4 is deformed to fall into the rim flange while receiving a large repetitive stress during running of the tire, so that the strain amplitude in the contact area becomes large and heats up to a very high temperature. It has been found that the synergistic action hardens or degrades the rubber properties of the bead portion, further generates a crack, and induces looseness at the folded portion of the carcass.

Therefore, in the present embodiment, the outer surface 4a of the bead portion 4 has a contact area T in contact with the flange arc surface Jf2.
By limiting (shown in FIG. 7) a specific range smaller than before, a rim flange J generated during tire running can be obtained.
The amplitude of strain and the frictional heat generated due to the deformation of the tire falling down to f can be reduced, and in addition to arranging the side packing rubber 9 and restricting the maximum main strain, it is intended to further suppress the occurrence of ply loose. Things.

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 FIGS. 1 and 7 in which the ratio (St / S) was variously changed was prototyped, and a drum durability test was performed.
When the temperature inside the bead portion (point A in FIG. 7) was measured, the ratio (St / S) was 0.2 to 0.2 as shown in FIG.
It has been found that by setting the range of 0.70, more preferably 0.4 to 0.65, and still more preferably 0.50 to 0.65, the heat generation of the bead portion 4 can be very small. is there.

If the ratio (St / S) is less than 0.2, the range of the contact area T becomes too small, and the amount of bending deformation of the bead portion 4 becomes remarkably large. The effect of prevention cannot be expected. Further, those having the ratio (St / S) of more than 0.70 are not much different from those of the conventional tire, and the frictional heat generation or strain amplitude due to the excessively large range of the contact area T is increased. No effect can be expected. The flange arc surface Jf
When 2 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 this embodiment, the outer surface of the bead portion 4 is a contact outer point P2 which is a radial outer point of a contact area T in contact with the flange arc surface Jf2 of the rim flange Jf.
, An arc-shaped curved surface portion 13 extending outward in the tire radial direction and projecting toward the tire lumen side. Such an arc-shaped curved surface portion 13 helps to reduce heat generation by further reducing the rubber gauge of the bead portion 4 and reducing internal friction of rubber.

The arcuate curved surface portion 13 is formed so as to protrude toward the tire cavity side, that is, to conform to the shape of the flange arcuate surface Jf2 of the rim flange Jf. When the rim falls down to the rim flange side and is deformed, the friction between the arcuate curved surface portion 13 and the flange arcuate surface Jf2 of the rim flange Jf becomes very small without arc reversal, so that the heat generation or distortion of the bead portion 4 This is preferable in that it can reduce the occurrence of looseness.

The radially outer end P3 of the arcuate curved surface portion 13 is, as shown in FIG.
From 15 to 35%, more preferably 20 to 30%, even more preferably 22 to 28% of the carcass sectional height Hc.
%, In this example, the height H5 is 21%, and the height H1 of the bead apex 8 is set to be substantially equal to the height H1. Further, in the present embodiment, the arc-shaped curved surface portion 9 is formed such that the intersection with the outer surface arc C1 of the sidewall portion 4 having the radius of curvature R1 centered on the tire lumen side and the intersection portion thereof appears as a ridge line in the tire circumferential direction. The intersections are illustrated.

If the radially outer end height H5 of the arcuate curved surface portion 13 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 13 and the rim The effect of reducing the friction of the flange Jf with the flange arc surface Jf2 tends to be reduced.
If it exceeds 0%, the rigidity of the bead portion 4 tends to decrease. Note that, as in this example, the outer end P3 of the arc-shaped curved surface portion 13
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 13 is preferably formed by a single or a plurality of arcs. When a single arc is used, the radius of curvature is adjusted to the carcass section height Hc. It is preferably set to 20 to 30%.
Further, as shown by a dotted line in FIG. 7, it is preferable to form the arc-shaped curved surface portion 9 and the outer circular arc of the sidewall portion 4 so as to be smoothly connected.

When such an arc-shaped curved surface portion 13 is formed, the amount of deformation of the bead portion 4 falling into the rim flange Jf becomes large. In particular, in the case of a heavy-duty tire mounted on a conventional 5 ° taper rim, the inner diameter of the bead seat surface 4b is set to be larger than the outer diameter of the rim seat surface Js, and the bead portion Because the interference was formed between the outer surface and the rim flange surface,
It is conceivable that the heat generated by the bead portion 4 is further increased because the bead seat surface 4b largely moves during the fall.

Therefore, as shown in FIG. 9, in the present embodiment, the inner diameter of the bead seat surface 4b is set to be smaller than the outer diameter of the rim seat surface Js in the dimensions in the tire vulcanizing mold indicated by a chain line. In the standard state, an example is provided in which an interference is provided between the bead seat surface 4b and the rim seat surface Js, thereby suppressing a large movement on the bead seat surface under load and suitably preventing rubber breakage and the like. ing. As a result, the heat generation level of the bead portion due to the repeated deformation can be reduced, the rubber breakage on the bead base surface can be suppressed, and the durability of the bead portion can be further improved.

As shown in FIG. 9, it is desirable that the maximum interference E between the rim seat surface Js on the fixed flange side and the bead seat surface of the tire having the entire inner dimensions is set to 0.5 to 3.0 mm. . If the amount of interference E is less than 0.5 mm, the effect of suppressing large movement on the bead seat surface 4b under load is small, and if it exceeds 3.0 mm, rim assembly becomes difficult. Further, a cord (fabric) chafer for reinforcing the bead seat surface 4b may be appropriately arranged.

Further, in the present embodiment, as shown in FIG. 10, a 60 ° position P of the flange arc surface Jf2 corresponding to a 60 ° arc angle from the radially outer end of the rim flange surface Jf1 in the flange arc surface Jf2. A line 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 4; The ratio to the line segment length F (f
/ F) is set such that the rubber gauge is determined to be 0.4 to 0.9.

As a result of the experiment by the present inventors, the looseness of the bead portion 4 is 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 on 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 them, the heat generation of the bead portion 4 can be controlled to prevent loosening.

That is, a tire having the structure shown in FIGS. 1 and 10 in which the ratio (f / F) was variously changed was prototyped and subjected to a drum durability test, and the temperature near the point M was measured. As shown in the above, when the ratio (f / F) exceeds 0.9, the rigidity of the bead 4 is increased, but the chance of contact with the rim flange Jf increases, the heat generation increases, and the ratio (f / F) increases. If) is less than 0.4, the rubber gauge of the bead portion is insufficient, so that the rigidity is reduced, the steering stability is reduced, and the structure may be destroyed.

As described above, regulating the rubber gauge of the bead portion also enhances the action of the side packing rubber 9,
It also helps to reduce the distortion in the region Y, and can further improve the durability of the bead portion.

The heavy-duty radial tire 1 according to the present embodiment has been described in detail. In any of the above-described embodiments, the cord made of the cord ply in which the organic fiber cord or the steel cord is arranged separately from the carcass ply 6 a in the bead portion 4. Examples in which the reinforcing layer is not provided are shown. This helps to reduce tire weight and reduce costs.

[0078]

EXAMPLE A heavy-duty radial tire for a 5 ° taper rim having a tire size of 10.00R20 was prototyped based on the specifications shown in Table 1 (Examples 1 and 2), and a durability test of a bead portion was performed. 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 portion (drum)> The sample tire was mounted on a regular rim of 7.50 × 20, and the internal pressure was adjusted to 1,000.
kPa, load 9000kgf, speed 20km / h
, The vehicle is stopped when damage that can be visually confirmed is generated, and the ratio L1 / L0 between the damage occurrence distance L1 and the complete running distance L0 (10000 km) is set to 100 in the conventional example. Evaluated by index. The higher the value, the better.

<Test for Measuring Maximum Principal Strain in Sidewall> As described above, the presence / absence of a peak and the maximum principal strain ε
m and εp were evaluated (regular rim: 7.50 × 20, internal pressure: 800 kPa).

<Crack Measurement Test> A sample tire mounted on a regular rim of 7.50 × 20 and filled with an internal pressure of 800 kPa was placed in an ozone chamber at an ozone concentration of 40 pphm and a room temperature of 40 ° C., and cracks occurred in the region Y. The time until the evaluation was evaluated using an index with the conventional example taken as 100.
The larger the value, the better the crack resistance.

<Tire Weight> The weight per tire is indicated by an index with the conventional example being 100. The smaller the value, the smaller the weight and the better. Table 1 shows the test results.

[0083]

[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. In the tire of the example, it was confirmed that the maximum principal strain εm did not have a peak point in the region Y and was 4.0% or less. Further, it was confirmed that (εm−εp) was less than 2% in each case, and that the relative strain difference was small. It can be seen that the tires of the examples have excellent crack resistance performance in correlation with the results. Note that substantially the same measurement results are obtained for other tire sizes.

[0085]

As described above, claims 1 to 3 are described.
In the invention described, by arranging the side packing rubber having a limited range of the modulus on the outer surface of the folded portion of the carcass, it is possible to reduce the difference in modulus between the carcass cord topping rubber and the like, thereby reducing distortion. And the bead durability can be improved by preventing looseness of the folded portion, and in particular, the durability of the bead portion of a heavy duty radial tire mounted on a 5 ° taper rim can be improved.

Since the outer end of the side packing rubber is located outside the outer end of the bead apex,
It is possible to prevent the carcass from being locally bent at the outer end of the bead apex, and to prevent the strength of the carcass cord from decreasing near the outer end of the bead apex. Further, by regulating the rubber modulus of the side packing rubber, the ability to follow the carcass is enhanced, and separation, ply loose and the like of the carcass can be effectively prevented.

According to the fourth aspect of the present invention, in addition to the above-described effects, the tire is assembled on a regular rim and the
When the inflation is changed from the provisional assembly state filled with the internal pressure of cm ² to the standard state filled with the normal internal pressure, the tire maximum width point P1, which is the outermost in the tire axial direction, and the radius of the contact area in contact with the rim flange. The maximum principal strain εm of the surface of the region Y between the inner point P2 which is the outward point in the direction is 4% or less, and the maximum principal strain εm of the region Y and the maximum principal strain εp at the tire maximum width point P1. By setting the difference (εm−εp) to less than 2%, the strain in the region Y can be reduced, so that generation of cracks can be effectively suppressed over a long period of time, and as a result, the cracks advance into the beads. To prevent pry loose from occurring.

According to the fifth aspect of the present invention, in addition to the above-mentioned effects, in the meridional section of the tire in a no-load state in which the tire is assembled to the regular rim and filled with the regular internal pressure, the outer surface of the bead portion is formed in the flange arc surface. By limiting the range of the contact area to contact, the amplitude of the strain and the frictional heat generated by the deformation of the tire that falls into the rim flange generated during tire running can be reduced, and the ply loose of the carcass turn-back part etc. can be effectively reduced. Can be suppressed.

According to the present invention, in addition to the above effects, 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 provided with the tire. By forming an arcuate curved surface that is convex toward the lumen side, the rubber gauge of the bead part is further reduced, heat generation and tire weight are reduced, and during running of the tire, the bead part moves to the rim flange side. Since the friction between the arcuate curved surface portion and the flange arcuate surface of the rim flange at the time of the deformation to fall down is extremely reduced, the heat generation of the bead portion can be further reduced, and the generation of looseness can be suppressed.

Further, by forming such an arcuate curved surface portion, the amount of deformation of the bead portion falling into the rim flange increases, but in the standard state, the interference between the bead seat surface and the rim seat surface is reduced. By providing
A large movement on the bead seat surface under load is suppressed, rubber breakage or the like is suitably prevented, and the heat generation level of the bead portion due to repeated deformation can be reduced, so that the durability of the bead portion can be further improved.

Further, in the invention according to claim 6, in the flange arc surface, 60 ° from the radially 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.

[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 sectional view taken along the line AA of FIG. 2;

FIG. 4 is a graph showing a measurement result of a maximum principal strain.

FIG. 5 is a diagram illustrating a method of measuring a maximum principal strain.

FIGS. 6A and 6B are diagrams illustrating a reference point position of a marking.

FIG. 7 is an enlarged sectional view of a bead portion showing another embodiment.

FIG. 8 is a graph showing a relationship between a temperature of a bead portion and a ratio (St / S).

FIG. 9 is a partial cross-sectional view illustrating an interference.

FIG. 10 is an enlarged sectional view of a bead portion showing another embodiment.

FIG. 11 is a graph showing a relationship between a temperature of a bead portion and a ratio (f / F).

FIG. 12 is an enlarged sectional view of a bead portion of a conventional heavy load 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 9 Side packing rubber J Regular rim Jf Rim flange Jf1 Rim flange surface Jf2 Flange arc surface

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuki Numata 13-1 Higashi Onuma, Shirakawa-shi, Fukushima Prefecture (72) Inventor Tsuneyuki Nakagawa 29-14, Kashiosha, Shirakawa-shi, Fukushima Prefecture (56) References JP Hei 9-66711 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 15/00 B60C 15/06

Claims (6)

(57) [Claims] A bead core is provided on a main body portion extending from a tread portion to a sidewall portion to a bead core of a bead portion. A carcass consisting of a carcass ply arranged at an angle of 70 to 90 ° with respect to the tire equator, and a bead apex extending in a tapered shape from the bead core to the tire radially outward between the body portion and the folded portion of the carcass. A heavy load radial tire, wherein the folded portion extends radially outward along an axially outer surface of the bead apex and is close to and parallel to the carcass body from the tire radially outer end of the bead apex. And a 100% modulus Mp of 47 on the outer surface in the tire axial direction of the folded portion. With arranging the side packing rubber of ~ 65kgf / cm ^2, topping the carcass code Gore
100% modulus Mt of rubber and side packing rubber
10 kgf / cm ² or less from 100% modulus Mp
A radial tire for heavy loads, characterized in that: 2. The bead portion has a 100% modulus Mc covering the outer surface of the side packing rubber in the tire axial direction and exposed to the outer surface of the bead portion and the bead seat surface.
７５75 kgf / cm ² chafer rubber is provided.
The side wall rubber having a modulus of 00% Ms of 10 to 20 kgf / cm ² is connected, and the parallel portion G
Is 2.0 to 8 times the maximum cross-sectional width CW of the bead core.
The radial tire for heavy load according to claim 1, wherein the radial tire is set to 0 times . 3. A height H2 of a radially outer end of the folded portion,
Wherein the carcass sectional 30-60% of the height Hc
The heavy duty radial tire according to claim 1 or 2, wherein 4. The tire is rim-assembled to a regular rim, and
When the inflation is changed from the provisional assembled state filled with kgf / cm ² of internal pressure to the standard state filled with normal internal pressure, the tire maximum width point P1 that is the outermost in the tire axial direction and the contact area that contacts the rim flange The maximum principal strain εm of the surface of the region between the contact outer point P2 which is the outer point in the radial direction is 4%
In addition, the difference (εm−εp) between the maximum principal strain εm in the region and the maximum principal strain εp at the tire maximum width point P1 is 2%.
The radial tire for heavy load according to any one of claims 1 to 3, wherein 5. The tire according to claim 5, wherein the tire is rim-assembled on a regular rim and is filled with a regular internal pressure under a no-load standard condition, and an outer surface of the bead portion is connected to a radially outer end of the rim flange surface of the rim flange so as to be approximately 90 °. The ratio (St / S) of the contact length St at which the outer surface of the bead portion contacts the flange arc surface and the arc length S of the flange arc surface while contacting the flange arc surface curved with an arc angle. ) Is 0.
The heavy load radial tire according to any one of claims 1 to 4, wherein the ratio is 2 to 0.70. 6. In the tire meridional section in the standard state, the bead portion has an interference between a bead seat surface and a rim seat surface and the ratio (St / S) is 0.2.
The outer surface of the bead portion extends radially outward from the contact outer point P2, which is the radial outer point of the contact area in contact with the rim flange, and is convex toward the tire bore. And 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 in the flange arc surface, and an axis of the carcass turning portion. When a line segment connecting the outer side surface in the direction with the shortest length F is an intersection point at which the bead portion outer surface intersects with N, a length f between the PNs;
The radial tire for heavy load according to claim 5, wherein a ratio (f / F) to the line segment length F is 0.4 to 0.9.