JPH10147116A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve air filling performance and to prevent excessive heat generation by preventing a bead toe from being raised or the locking point of a carcass ply from being raised by the bulging of a bead part. SOLUTION: A rubber filler 4 is formed by a hard rubber filler 4a having rubber hardness of not less than 85 and a soft rubber filter 4b having rubber hardness of 65 to 75. Letting an outside contact point of a bead cover 3a and a carcass topping rubber be A and an inside contact point thereof be B, an outside contact point C of the hard and soft rubber fillers 4a, 4b is set above the position of a rim flange Rd and below not less than 10mm from the winding end D of the carcass and a distance Lb between the contact point B and an inside contact point E of the hand and soft rubber fillers 4a, 4b is set at not more than 1.5 La, where La is a distance between the contact point A and the contact point C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic radial tire for heavy loads.

[0002]

2. Description of the Related Art Generally, as shown in FIGS. 4 and 5, a pneumatic radial tire has at least one layer of a carcass ply (1) having a cord arrangement in a radial direction. Both ends are wound up from the inside to the outside around the bead core (3) and the rubber filler (4) disposed thereon at the bead portions (2) on both sides and are locked. Further, the locking portion is reinforced by disposing a bead portion reinforcing layer (5) called chafer having steel or organic fiber cord.

On the outside of the carcass ply (1) in the tread portion (7), one or a plurality of belt layers (8) are provided.
The carcass layer (1) and the belt layer (8)
A rubber layer such as a sidewall and a tread rubber is adhered to the outside of the tire and integrally formed to form a tire. (9)
Is a main groove provided on the outer peripheral surface of the tread portion (7).

[0004]

By the way, in the case of a tire subjected to high internal pressure filling and high load, the bead portion overhangs around the bead heel portion fixed by the rim flange.

That is, when the bead core (3) is formed of an aggregate of bead wires having a circular cross section, the tension of the carcass ply (1) subjected to a high internal pressure rotates the inner end of the bead core from the tire radial direction to the outside. Generate a moment.

This will be described by replacing the stress distribution in the cross section of a bead core having a hexagonal cross section with the truss structure of FIG.

[0007] The carcass ply tension in the tire radial direction acting on the inner end of the bead core (the inner surface side end of the tire),
A compressive stress is generated in the upper outer peripheral layer of the bead core (3), and this force is dispersed by point contact between the outer peripheral wires (30). The moment generated by the contact between the outer peripheral wires acts to lift the inner end of the bead core, so the tensile stress is mainly applied inside the core, and the carcass ply tension is not dispersed, and the lift near the inner end of the core is raised. The stress that concentrates on the broken wire causes the bead core to collapse. In addition to this, the tire grows while bending due to rolling of the tire deforms the bead portion outward.

For this reason, as shown in FIG. 5, the bead portion (2) projects outward, and accordingly, the bead toe portion (2a) is centered on the bead heel portion (2b) fixed to the rim flange (10). Is in a raised state (a chain line in FIG. 5).

Such overhang deformation of the bead portion is as follows.
It increases the strain inside and outside the bead, lowers the bead durability, impairs renewability, and causes surface cracks outside the bead. Further, the floating deformation of the bead toe portion (2a) reduces the contact area between the rim flange (10) and the tire bead, lowers the air sealing property at the time of filling the internal pressure, and makes the air filling operation difficult.

In particular, as shown in FIG. 5, in the case of a tire having a conventional structure using a relatively soft kind of rubber as the rubber filler (4) of the bead portion (2), sufficient rigidity cannot be obtained. The problem has become prominent.

In recent years, a rubber filler (4) comprising a combination of a hard rubber filler and a soft rubber filler has been proposed for the purpose of suppressing deformation and improving durability by improving the rigidity of the bead portion (for example, Japanese Patent Laid-Open No. 2-133208). JP-A-6-64412). In the rubber filler (4) having this structure, the hard rubber filler (4a) is arranged adjacent to the bead core (3) as illustrated in FIG.

By the way, in order to effectively disperse the force of the overhanging deformation of the bead portion (2) to the rim flange (10), the hard rubber filler (4a) must be at least as high as the rim flange (10). Although it is desirable to dispose, when the bead portion (2) is mounted on the rim, the bead portion deformation due to the rolling of the tire occurs above the rim flange (10). If it exists at a very high position, the hard rubber filler (4
The movement of a) also increases accordingly. The heat generated by the movement of the rubber increases as the hardness of the rubber increases.
Deterioration of rubber strength occurs and causes failure such as separation.

In particular, as shown in FIG.
If the inner end of a) is set high, the movement of the hard rubber filler generated by rolling becomes large, so that the calorific value inside the bead increases, which adversely affects the bead durability and promotes the deterioration of rubber. There's a problem.

Therefore, when a rubber filler obtained by combining a hard rubber filler and a soft rubber filler is used,
It is desirable to set the height of the bead portion so that the overhanging deformation force can be effectively distributed to the rim flange, and the bead portion can be degraded by heat without deteriorating the flexibility of the bead portion.

However, this type of conventional rubber filler is not sufficiently satisfactory in actuality because no consideration has been given to both the prevention of overhanging deformation and the prevention of heat generation.

The present invention has been made in view of the above, and as a structure of a rubber filler formed by a combination of a hard rubber filler and a soft rubber filler, the overhanging force of the bead portion can be effectively dispersed to the rim flange, It is effective in suppressing the floating of the bead toe portion, and further suppresses an increase in the amount of heat generated by providing the hard rubber filler, thereby preventing rubber deterioration and durability deterioration due to heat generation.

[0017]

According to the present invention, a single carcass ply made of a steel cord is wound from the inside to the outside around a bead core and a rubber filler disposed thereon at a bead portion. In the heavy duty pneumatic radial tire that is locked, the rubber filler is composed of a hard rubber filler having a rubber hardness of 85 or more adjacent to a bead core and a soft rubber filler having a rubber hardness of 65 to 75 continuous with the hard rubber filler. In the cross-sectional shape of the tire, when the interface point on the outer surface side of the tire between the bead cover surrounding the entire bead core and the carcass stopper rubber is (A), and the interface point on the inner surface side is (B), a hard rubber filler and a soft rubber filler are used. Is higher than the height of the rim flange diameter and the carcass is wound The distance (Lb) from the interface point (B) to the interface point (E) on the inner surface side of the tire between the hard rubber filler and the soft rubber filler is 10 mm or more lower than the end (D). The distance (La) from the point (A) to the interface point (C) is set to 1.5 La or less.

In the above configuration, the interface point (C) on the tire outer surface side and the interface point (E) on the tire inner surface side are set as described above because of the effect of dispersing the force of bead overhang deformation and the effect of hardening. This is to achieve both the effect of suppressing the heat generation of the rubber filler.

That is, the interface point (C) on the tire outer surface side between the hard rubber filler and the soft rubber filler is set higher than the rim flange diameter in order to effectively disperse the deformation stress of the bead portion to the rim flange. Is preferred, but
On the other hand, if the interface point (C) is too high, the boundary due to the difference in rigidity between the hard rubber filler and the soft rubber filler due to the overhang deformation due to running growth not only appears in the bead portion appearance but also causes the tire to roll. The resulting deformation of the tire side portion is hindered, causing an increase in rolling resistance, and the hard rubber filler is likely to generate heat.

Therefore, as described above, the interface point (C)
Is preferably higher than the diameter of the rim flange and at least 10 mm lower than the winding end (D) of the carcass ply.

On the inner surface of the tire, the overhang deformation is maximized at the intersection of the straight line passing through the winding end (D) of the carcass ply and orthogonal to the carcass line with the inner surface of the tire and slightly above the tire. The higher the position of (E), the closer to the above-mentioned region of large deformation, the greater the movement of the hard rubber filler due to the above-mentioned deformation associated with the rolling, and the more heat is generated. Therefore, in order to prevent excessive heat generation, the distance (Lb) is preferably set to 1.5 La or less, particularly preferably 1.0 La or less.

The above interface point (C) is defined in claim 2
It is particularly preferable to set the position at a position higher than the height position of the rim flange diameter by 5 mm or more from the viewpoint of the effect of dispersing stress on the rim flange and the effect of suppressing rolling resistance.

The ratio of the amount of the hard rubber filler to the total amount of the rubber filler is preferably 30% or less. That is, when the ratio of the hard rubber filler amount exceeds 30%, the effect of improving the rigidity of the bead portion is obtained, but heat is easily generated accordingly, so it is preferable to set the ratio to 30% or less as described above.

[0024]

According to the pneumatic radial tire having the above structure, the rubber filler disposed on the bead core is composed of a combination of a hard rubber filler and a soft rubber filler. Proper rigidity can be ensured, so that the overhanging deformation of the beat portion and the rising deformation of the bead toe portion due to the traveling growth can be suppressed.

In particular, by setting the interface point (C) on the outer surface of the tire between the hard rubber filler and the soft rubber filler as described above and setting it higher than the height of the rim flange diameter, the bead overhang deformation is reduced. The force can be effectively distributed by the rim flange via the hard rubber filler. As a result, excessive overhanging deformation of the bead portion due to traveling growth can be suppressed, and floating of the bead toe portion can be reduced.

Moreover, the interface point (C) on the tire outer surface side is set to be 10 mm from the winding end (D) of the carcass ply.
The distance (Lb) between the interface point (E) and the interface point (B) on the inner surface side of the tire is set to be lower than the interface point (A).
1.5La of the distance (La) from the interface point (C) to the interface point (C)
By setting below, the hard rubber filler is located at a lower position away from the region of large deformation due to the rolling on the inner surface side of the bead portion, the movement of the hard rubber filler is not so large, and excessive hard rubber filler Heat generation can be suppressed. In addition, it does not hinder deformation of the tire side portion due to rolling, and does not cause an increase in rolling resistance.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

1 to 3 are sectional views of a bead portion according to an embodiment of the present invention.

(1) A carcass comprising a single layer of plies in which steel cords are arranged in the tire radial direction,
(2) is a bead core, and (3) is a bead core composed of an aggregate of bead wires located at the center of the bead part. A rubber layer called a bead cover (3a) surrounding the entire core is provided around the bead core (3). (4) is a rubber filler having a substantially deformed triangular cross section which is provided on the bead core and extends in the tire radial direction, and (5) is a bead portion reinforcing layer called a chafer having a steel cord or an organic fiber cord. FIGS. 1 to 3 show a case where the bead portion reinforcing layer (5) is composed of three reinforcing layers having an organic fiber cord. (6) indicates a strip rubber.

The rubber filler (4) has a rubber hardness adjacent to the bead core (3) of at least 85, more preferably at least 90, and more preferably at least 90 (hardness according to JIS k6301). Rubber filler (4
a) and a soft rubber filler (4b) made of the softer rubber material having a rubber hardness (same hardness as described above) of 65 to 75 continuous with the hard rubber filler (4a).

The rubber hardness of the hard rubber filler (4a) is 8
When the value is 5 or less, the effect of maintaining rigidity by using a hard rubber material is reduced, so that the value is set as described above. When the rubber hardness of the soft rubber filler (4b) is higher than the above range, the rigidity becomes too high, causing a problem of heat generation. When the rubber hardness is lower than the above range, the expected rigidity cannot be obtained. Is good.

As shown in the figure, the carcass ply (1) is wound along the tire outer surface of the rubber filler (4) and its ply end is wound up from the inside to the outside with respect to the bead core (3) and locked. (1a) shows the winding portion, and (D) shows the winding end.

The winding portion (1a) may end at a position above the rubber filler (4), but as shown in the figure, the winding portion (1a) ends at a position below the upper end of the rubber filler (4). The effect of the upper end of the tire does not appear on the tire surface, which is more preferable. In this case, bead core (3)
At least 10 mm from the upper end of the tire (outer end in the tire radial direction)
It is set to have about the same height. That is, if it is smaller than this, the locking effect by winding cannot be sufficiently obtained.

Carcass ply of tire tread (1)
One or more belt layers are arranged on the outside of the tire as before, and a belt reinforcing layer is further arranged as necessary. Further, a plurality of belt layers are arranged on the outer peripheral surface of the tire with the tread rubber in the tire circumferential direction. Is formed.

The hard rubber filler (4a) and the soft rubber filler (4b) constituting the rubber filler (4) are set so that the interface between them satisfies the following condition.

In the cross-sectional shape of the tire, the interface point on the tire outer surface side between the bead cover (3a) wrapping the entire bead core (3) and the topping rubber of the carcass ply (1) is (A), and the interface point on the tire inner surface is (A). B), the interface point (C) on the tire outer surface side between the hard rubber filler (4a) and the soft rubber filler (4b) is the radial height of the rim flange diameter, that is, the outer diameter (Rd) of the rim flange (10). End of carcass ply (D)
It is set so that it is at a height position that is at least 10 mm lower.
From the viewpoint of the effect of stress dispersion, the interface point (C) is preferably set at a position higher than the height of the rim flange diameter (Rd) by 5 mm or more.

The distance (Lb) from the interface point (B) to the interface point (E) on the inner surface side of the tire between the hard rubber filler (4a) and the soft rubber filler (4b) is defined as the interface point (A). (La) from to the winding end (D)
Is set to 1.5 times or less (including the case where it coincides with the interface point (B)), preferably 1.0 La or less so as not to be higher than the interface point (C) on the tire outer surface side. With this setting, heat generation of the hard rubber filler can be prevented.

The interface connecting the inner and outer interface points (E) and (D) may be substantially linear or slightly curved as shown in the figure, or may be deformed in a zigzag, wavy or irregular shape in cross section. May be done.

The volume of the hard rubber filler (4a) may exceed 30% of the total amount of the rubber filler (4) in some cases.
More preferably, it is better to set it to 20% or less.

In the pneumatic radial tire having the above-described structure, an appropriate bead portion rigidity can be secured by the hard rubber filler (4a) arranged adjacent to the bead core (3), and the pneumatic radial tire accompanies internal pressure filling and running growth. Overhanging deformation of the bead portion and floating deformation of the heel toe portion can be suppressed.

In particular, the interface points (E) and (C) on the inner and outer sides of the tire between the hard rubber filler (4a) and the soft rubber filler (4b) connected thereto are set as described above. In particular, since the outer interface point (C) is higher than the height of the rim flange diameter (Rd), the deformation stress applied to the hard rubber filler (4a) can be supported by the rim flange (10). The stress can be dispersed to the rim flange (10), so that the overhanging deformation and the heel-toe portion floating deformation accompanying the traveling growth can be suppressed.

On the other hand, on the inner surface of the tire, the distance (Lb) from the inner interface point (E) to the interface point (B) is set to 1.5 La or less, which is the outer distance La, to allow the tire to roll. Hard rubber filler (4a)
Does not exist, and on the outer surface of the tire, the outer interface point (C) is connected to the winding end (D) of the carcass ply (1).
Since the hard rubber filler (4a) is provided at a position lower by 10 mm or more, the movement of the hard rubber filler (4a) during traveling does not become large, and the generation of high heat generation can be prevented. Further, concentration of stress strain at the ply end can be prevented, and further, an increase in rolling resistance can be prevented.

The above effects are apparent from the results of the following comparative test.

As examples, the bead portion reinforcing layer, the hardness of the rubber filler and the ratio of the amount of the hard rubber filler, the outer interface point (C) and the inner interface point (E) between the hard rubber filler and the soft rubber filler are defined as follows: A bead-structured tire shown in FIG. 1 (Example 1) and a bead-structured tire shown in FIG. 2 (Example 2), each set as shown in Table 1 below.
And a tire having a bead structure shown in FIG. 3 (Example 3), a heavy load durability test was performed as described below, a bead portion heat generation temperature was measured, and an air filling property test was further performed.

For comparison, a conventional tire having a bead structure shown in FIG. 5 in which the rubber filler is made of a single rubber, and the hardness of the bead portion reinforcing layer and the hardness of the rubber filler are set as shown in Table 1 below (comparison). Example 1) and the rubber filler (4) is composed of a combination of a hard rubber filler (4a) and a soft rubber filler (4b), and has a rubber hardness, an outer interface point (C) between the hard rubber filler and the soft rubber filler, and The inner interface point (E) and the bead structure tire (Comparative Example 2) of FIG. 7 and the bead structure tire (Comparative Example 3) of FIG.
Similarly, a heavy load endurance test was performed, a bead portion heat generation temperature was measured, and an air filling test was further performed.

Here, the tires of the example and the comparative example were tires having a size of 11R22.514PR, and the same conditions were used for all other structures except for a bead portion such as a belt structure.

In the heavy load durability test, the tire internal pressure was set to 90
The vehicle traveled up to the fault at 0 kPa, a load of 210%, and 25 km / h, and the traveling distance was displayed.

For the measurement of the exothermic temperature, the bead temperature was measured after running for 5 hours under the same test conditions as described above. The measurement point was the rear surface of the carcass ply (point (G) in the figure) on a line perpendicular to the carcass line from the winding end (D) of the carcass ply.

The air filling test was carried out at a specified load and internal pressure according to the size of the tire at a speed of 88 km / h for 12 hours, and then mounted on a 22.5 / 7.50 rim. The evaluation was performed in three stages of ◎ ○ ×, and ○ indicates that there is no problem in the filling property, ◎ indicates that the filling property was superior, and × indicates that the filling property was inferior, and the test results are shown in Table 1. Was.

[0050]

[Table 1] As is clear from the above test results, in the case of the conventional tire of Comparative Example 1, the problems of bead portion overhang deformation and lifting of the bead toe portion were large, and the air filling property was deteriorated. In the case of Comparative Example 2 in which the hard rubber filler and the soft rubber filler were combined and the position of the interface point (E) on the inner side of the tire was set high, the air filling property was improved, but the heat generated by the behavior of the hard rubber filler was improved. Increased, and the durability decreased. In the case where the interface point (E) of the hard rubber filler on the outer surface side and the inner surface side of the tire was set low as in Comparative Example 3, the effect of suppressing overhang deformation and floating was small, and there was a problem in air filling properties. .

On the other hand, in the case of Examples 1 to 3 of the present invention, the effect of suppressing the protrusion deformation of the bead portion and the lifting of the bead toe portion due to the running growth is excellent, the air filling property is excellent, and the rolling of the tire is excellent. The movement of the hard rubber filler due to the deformation caused by the deformation is small, and excessive heat generation can be suppressed.

[0052]

As described above, according to the pneumatic tire of the present invention, as the rubber filler in the bead portion, a combination of a hard rubber filler and a soft rubber filler is provided.
In particular, by setting the interface between the hard rubber filler and the soft rubber filler as in the invention of claim 1, the rigidity of the bead portion is appropriately high, and the overhanging deformation due to running growth and the lifting deformation of the bead toe portion can be reduced. . The air filling property can be improved. In addition, since the height of the hard rubber filler is limited and the interface point on the inner surface side of the tire is set so as not to be higher than a certain level, excessive heat generation due to the movement of the hard rubber filler can be suppressed, and the rolling resistance increases. There is no.

In particular, the above-mentioned effect becomes more remarkable when the inner interface point (E) is set as in claim 2 and the ratio of the hard rubber filler is set as in claim 3. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a bead portion showing one embodiment of the present invention.

FIG. 2 is a sectional view of a bead portion showing another embodiment of the present invention.

FIG. 3 is a sectional view of a bead portion showing still another embodiment of the present invention.

FIG. 4 is a sectional view schematically showing a general pneumatic radial tire.

FIG. 5 is a cross-sectional view showing a bead structure having a single rubber filler of a conventional tire.

FIG. 6 is an explanatory diagram of a stress distribution in a cross section of a bead core.

FIG. 7 is a cross-sectional view showing a conventional bead structure including a rubber filler obtained by combining a hard rubber filler and a soft rubber filler.

FIG. 8 is a cross-sectional view showing another conventional bead structure including a rubber filler obtained by combining a hard rubber filler and a soft rubber filler.

[Explanation of symbols]

(1) Carcass ply (1a) Hoisting ply part (2) Bead part (2a) Bead toe part (3) Bead core (3a) Bead cover (4) Rubber filler (4a) Hard rubber filler (4b) Soft rubber filler (5) Bead part reinforcing layer (10) Rim flange (A) Outer interface point between bead cover and carcass stopping rubber (B) Inner interface point between bead cover and carcass stopping rubber (C) Hard rubber filler and soft rubber filler (D) Rolled end of carcass ply (E) Inner interface between hard rubber filler and soft rubber filler

Claims (3)

[Claims] 1. A pneumatic radial tire in which one carcass ply made of a steel cord is rolled up and locked from inside to outside around a bead core and a rubber filler disposed thereon at a bead portion, wherein the rubber filler is , Rubber hardness 8 adjacent to bead core
A hard rubber filler of at least 5 and a soft rubber filler having a rubber hardness of 65 to 75 continuous with the hard rubber filler, and in the cross-sectional shape of the tire, an interface between a bead cover enclosing the entire bead core and the carcass stopping rubber on the tire outer surface side When the point is (A) and the interface point on the inner surface is (B), the interface point (C) on the outer surface of the tire between the hard rubber filler and the soft rubber filler is higher than the height position of the rim flange diameter and the carcass. The distance (Lb) from the interface point (B) to the interface point (E) on the inner surface side of the tire between the hard rubber filler and the soft rubber filler is 10 mm or more lower than the winding end (D). A pneumatic radial tire for heavy loads, wherein the distance (La) from the interface point (A) to the interface point (C) is set to 1.5 La or less. 2. The pneumatic radial for heavy loads according to claim 1, wherein the interface point (C) on the outer surface of the tire between the hard rubber filler and the soft rubber filler is at least 5 mm higher than the height of the rim flange diameter. tire. 3. The pneumatic radial tire for heavy loads according to claim 1, wherein the amount of the hard rubber filler is 30% or less of the total amount of the rubber filler.