JP3377462B2 - Heavy duty pneumatic tires - 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 pneumatic tire having a bead portion with improved durability and reduced weight.

[0002]

2. Description of the Related Art Heavy duty pneumatic tires used for large vehicles such as trucks and buses employ a carcass ply in which a large number of steel cords are arranged in parallel in order to maintain a high internal pressure. In such a heavy duty pneumatic tire, strain is likely to be concentrated at the end of the folded portion of the carcass due to repeated bending deformation at the sidewall portion and the bead portion during traveling.

Further, a tensile force inwardly in the tire radial direction is applied to the folded portion of the carcass due to the tension of the carcass due to a high internal pressure, and the cut end of the steel cord does not have a rubber component and plating for cross-linking adhesion. The adhesiveness with the components is poor, so that the folded end of the carcass is likely to peel off from the rubber, and such peeling reduces the durability of the tire.

In order to prevent such breakage of the folded back portion of the carcass, Japanese Patent Laid-Open Publication No. 6-119240 reinforces the carcass layer a folded back by the bead core 5 so as to further wrap around the outside thereof, as shown in FIG. It is proposed to arrange the layer b to prevent bead deformation and increase the rubber gauge outside the bead portion. The reinforcing layer b includes organic fiber cords and steel cords.

By the way, according to this proposal, since the reinforcing layer b is folded back in the axial direction of the tire, a peeling phenomenon is likely to occur from the end portion bi of the folded back portion of the reinforcing layer in the axial direction of the tire. Therefore, Japanese Patent Laid-Open No. 10-147117 discloses that the inner end portion bi is located on the inner side in the tire radial direction of the bead core so as to prevent the peeling phenomenon caused by the inner end portion and to the inner side in the tire axial direction of the bead portion. In order to prevent damage near the end of the carcass due to an increase in bead deformation due to a decrease in bead rigidity due to the absence of the reinforcing layer, it is necessary to dispose a cap member at the outer edge of the carcass and the reinforcing layer. is suggesting.

[0006]

SUMMARY OF THE INVENTION
This yard structure proposed by Japanese Patent Publication No. 10-147117 can reduce bead damage and reduce the amount of a reinforcing layer, and thus can achieve weight reduction of a tire. However,
By disposing the cap member described above, the number of tire manufacturing steps is increased and the productivity is reduced. Further, it is not possible to sufficiently prevent an increase in strain near the end portion of the carcass, which is caused by a decrease in bead rigidity due to the absence of the reinforcing layer in the axially inner portion of the tire bead portion and an accompanying increase in bead deformation.

The present invention is based on the idea that the strain in the vicinity of the end of the carcass where the inner portion in the tire axial direction is eliminated in the bead portion can be reduced by adjusting the thickness distribution of various members. An object of the present invention is to provide a heavy-duty pneumatic tire in which the durability of the bead portion is improved and the weight thereof is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention is a tread portion.
From (2) through the sidewall part (3) to the bead core (5) of the bead part (4), fold back around the bead core (5) from the inner side to the outer side in the axial direction of the tire. Carcasses made of ply with radial construction (6)
And a bead apex (8) arranged between the body portion 6a and the folded portion 6b of the carcass, and bead reinforcement using a ply formed by arranging cords in parallel with each other while passing outside the folded portion 6b in the tire axial direction. In a normal state in which the bead reinforcing layer (9) is fitted to the regular rim R and a regular internal pressure is applied, the edge 9E on the outer side in the tire axial direction of the bead reinforcing layer (9) has a carcass turning end 6E. Bead reinforcement layer on the inside of the tire in the radial direction
The edge 9F on the inner side in the tire axial direction of (9) is a bead core (5).
Is located radially inward of a straight line N connecting the innermost end 5Q and the outermost end 5P in the tire axial direction, and the carcass turn-up end 6E and the edge 9E on the outer side in the tire axial direction of the bead reinforcement layer (9). The distance h in the tire radial direction is set to 5 mm or more and 20 mm or less, and the shortest distance A passing through the carcass folding end 6E between the contour line o of the tire outer surface and the contour line i of the tire inner surface and the carcass from the carcass folding end 6E. The ratio of the shortest distance B that draws a perpendicular to the main body 6a of the above and the shortest distance C that draws a perpendicular from the carcass folding end 6E to the outline o of the outer surface is 0.35 ≦ B / A ≦
The pneumatic tire for heavy loads is characterized by the relationship of 0.55, 0.25 ≤ C / A ≤ 0.40, and 1.00 ≤ B / C ≤ 1.80.

By organically combining and integrating such a structure, the durability of the bead portion can be improved.

It is also possible to arrange at least three rubber layers on the perpendicular line from the carcass turn-up end 6E to the contour line o of the tire outer surface, and at least three rubber layers. From the carcass turn-up end 6E toward the contour line o, the first layer (1
0), the second layer (11), the third layer (12), and the first layer (10)
Thickness c1, second layer (11) thickness c2, and third layer (12) thickness c3, 0.08 ≦ c1 / C ≦ 0.38, 0.04 ≦ c2 / C ≦ 0.20, 0.30 ≦
The relationship can be c3 / C ≦ 0.75 and c2 ≦ c1 ≦ c3.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a heavy duty pneumatic tire 1 is a tubeless tire for trucks and buses, which is mounted on a rim R having a 15 degree taper in this example,
Therefore, this example shows a normal state in which the "normal rim" R having a 15 ° taper is fitted and the "normal internal pressure" is applied.

In the present specification, the "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATMA.
If it is a standard rim, it is “Design Rim” for TRA, or “Measuring Rim” for ETRTO. In addition, "regular internal pressure" is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure, and for TRA, the table "TIRE LOAD AT VARIOUS" COLD INFLATION PRESSU
"INFL" is the maximum value described in "RES" or ETRTO
ATION PRESSURE ", but 180 kPa if the tire is for passenger cars.

A heavy duty pneumatic tire (hereinafter referred to as tire 1) has a tread portion 2, sidewall portions 3 and 3 extending inward from both ends thereof in a radial direction of the tire, and these sidewall portions 3 and 3. It has a hollow toroidal shape having a pair of bead portions 4 and 4 located inward in the radial direction. The tread portion 2 to the sidewall portion 3 are formed.
To the body portion 6a passing through to the bead core 5 of the bead portion 4,
A carcass ply 6A having a radial arrangement in which the bead core 5 is folded back from the inner side in the axial direction of the tire to be wound up and has a folded-back portion 6b extending to a carcass folded-back end 6E.
Consists of.

The carcass 6 is composed of a single or a plurality of carcass plies 6A in this example, and the carcass ply 6A is formed by arranging a large number of cords in parallel. The angle of these cords is the tire equatorial plane C
In contrast, they are arranged at an angle of 85 to 90 °. As the cord, a twisted steel filament is preferably used. Further, the belt layer 7 and the bead reinforcing layer 9 which are known to the outside of the carcass in the radial direction and inside the tread portion 2, the outside of the bead core 5 in the radial direction and the carcass 6 are formed.
Stand up between the main body part 6a and the winding part 6b according to JIS A
A bead apex 8 having a triangular cross section made of rubber having a hardness of 50 to 65 degrees is provided. In this example, the belt layer 7 is composed of four layers of steel cord belt plies.

In the bead reinforcing layer 9, the main portion on the outer side in the tire axial direction extends outward in the tire radial direction along the outside of the folded portion 6b of the carcass, and the sub portion on the inner side in the tire axial direction is formed. It extends along the folded-back portion 6b of the carcass and terminates in the bead rubber apart from the folded-back portion 6b in the vicinity of the lowermost end of the folded-back portion 6b without wrapping the outside.

The bead reinforcing layer 9 is formed by a ply in which a reinforcing layer cord made of steel cords arranged at an intersecting angle of 20 to 40 degrees with respect to the carcass cord is covered with topping rubber on both sides. If the angle is less than 20 °, the carcass cord 6A and the reinforcing layer cord are likely to move in the same manner, and the effect of increasing the rigidity of the bead portion is small.
If it exceeds 0 °, the difference between the bending direction of the bead portion and the direction of the reinforcing layer cord becomes excessive, and the effect of resisting the bending of the bead is reduced.

Further, the distance h in the tire radial direction between the end edge 9E of the main portion on the outer side in the axial direction of the tire and the carcass folding end 6E is set to be 5 mm or more and 20 mm or less. By thus setting the distance h of 5 to 20 mm, it is possible to reduce the occurrence of a rigidity step on the outer wall of the tire. If the distance h is less than 5 mm, the ends of the two plies form an integral step, and there is a risk that a rigidity step may occur, causing damage from both ends. If the distance h exceeds 20 mm, the bead portion of the bead reinforcement layer The effect of increasing the rigidity is reduced, the effect of reducing the strain applied to the carcass folded-back end 6E at the time of loading by the bead reinforcing layer 9 is reduced, and the carcass folded-back end 6E is easily damaged.

On the other hand, the edge 9F of the auxiliary portion on the inner side in the tire axial direction is located radially inward of the straight line N connecting the innermost end 5Q and the outermost end 5P of the bead core 5 in the axial direction of the tire. . In this way, the bead reinforcing layer 9 rises from the bottom of the bead portion 4 to the outer side in the tire axial direction without wrapping the bead core 5, thereby preventing a peeling phenomenon starting from the tire axially inner end 9F of the reinforcing layer. In addition, the weight of the tire can be reduced, and the excessive rigidity caused by providing the bead reinforcing layer 9 can be alleviated to facilitate the rim assembly work.

The wire diameter of the bead reinforcing layer 9 is, for example, tire size 11R22.5 with respect to the carcass cord.
In the case of 80-140%, such as tire size 38
In the case of 5 / 65R22.5, about 70 to 130% is adopted.

Further, as shown in FIG. 2, the sidewall portion 3
Is provided with sidewall rubber layers 10 and 10 that extend to the bead portion 5 and form the outer surface of the tire, and a chafer 11 that extends from the inner side in the radial direction of the bead core 5 in contact with the flange portion of the rim R. In the chafer 11, the sidewall rubber layer 10 is located outside in a height region that exceeds the flange of the rim and forms an overlapping region where the sidewall rubber layer 10 overlaps with the boundary surface M. Further, the sidewall rubber layer 10 is made of rubber having excellent weather resistance and bending fatigue resistance, and the chafer 11 is made of rubber that is resistant to abrasion with the rim flange. These two different rubber layers are joined at the boundary surface M so as not to separate due to bending deformation.

By adjusting the thickness distribution among the inner surface of the tire, the folded-back portion 6b of the carcass, the main body portion 6a of the carcass, and the outer surface of the tire, the strain near the end portion of the carcass is reduced and the durability of the bead portion is reduced. Increase. For this reason, as shown in FIG. 2, with the length of the shortest line segment M1 passing through the carcass turning-back end 6E between the contour line o of the tire outer surface and the contour line i of the tire inner surface. A certain shortest distance is A, and a perpendicular line M from the carcass folding end 6E to the carcass body 6a.
Let B be the shortest distance to drop 2 and C be the shortest distance to drop the perpendicular line M3 from the carcass folding end 6E to the contour line o of the outer surface. Here, the contour line refers to a line that smoothly connects small irregularities on the tire inner surface and the tire outer surface with a reference line passing through the sidewall portion, the bead portion, or the inner surface to contour each surface.

The tire 1 has the above-mentioned A, B, and C with 0.35≤B / A≤0.55, 0.25≤C / A≤0.40, and 1.00≤.
The shapes of the carcass folding end 6E and the bead apex 8 are set so as to satisfy the relationship of B / C ≤1.80.

When B / C is less than 1.00, the carcass folding end 6E comes too close to the carcass body 6a, and when the bead portion is bent and deformed, the carcass folding end 6E, that is, the carcass cord. The tip end of the filament of the steel cord forming the stab penetrates into the rubber portion of the bead apex 8, and the steel cord and the rubber are broken at the end thereof. Also, B / C
When the value of exceeds 1.80, the carcass folding end 6E becomes
It is too close to the outer contour line o in the tire axial direction. That is, generally, the strain proportional to the distance from the neutral line of the bending deformation becomes large, and the breakage easily occurs.

The same can be said for the ratio of A, B, and C, which represents the thickness of the entire bead portion. That is, B
/ A exceeds 0.55, and C / A is 0.25
When the B / A is less than 0.35 and the C / A exceeds 0.40, the carcass folding end 6E has a large strain due to bending deformation. The tip of the steel cord filament forming the carcass cord is stuck into the rubber portion.

Here, the contour line o of the outer surface of the tire,
The shortest distance A between the contour i of the tire inner surface is, for example, in the case of a truck / bus tire, a tire size of 1
1R22.5 is about 25 to 30 mm, tire size 385 / 65R22.5 is about 20 to 32 mm, the flange height is about 1.5 to 2.5 times, and other types of tires Can be defined similarly.

Further, as shown in FIG. 3, a structure in which at least three rubber layers are arranged on the perpendicular line M3 between the carcass folding end 6E and the tire axial outer contour line o is the carcass folding end 6E. It has been found to be effective in reducing the distortion between the steel filament / rubber part of. Three rubber layers, from the carcass folded end 6E,
The first layer 21, the second layer 22, and the third layer 23 are arranged on the outer side in the tire axial direction toward the contour line o, and the fourth layer is formed on the outermost side.
Layer 24 can be included.

The first layer 21 is formed by the carcass folding end 6E.
And extends outward along the bead apex 8 in the radial direction while covering the outer edge 9E of the bead reinforcing layer 9 and ends in a tapered shape below the upper end of the bead apex 8. Further, the second layer 22 in this example is a sheet-like rubber layer extending radially outward from the point between the bead core 5 and the upper end of the flange along the second layer 22 and beyond the second layer. The JIS hardness A of the first layer 21 is 60 to 78 °. The second layer 22 is made of soft rubber and exhibits a cushioning function. The second layer 22 has a JIS hardness A of 55 to 78 [deg.], Preferably 55 to 65 [deg.], In order to alleviate the stress acting on the carcass folded-back end 6E due to the compression from the rim flange.

The third layer 23 is an extension of the chafer 11, and is made of hard rubber that maintains the contact strength with the flange and prevents bead deformation. When the compound is a hard compound and the IS hardness A is small, bending occurs at the carcass folded-back end 6E to cause cracks and filler edge loosening, while if the hardness is excessively large in the third layer 23. Since cracks occur, the JIS
The hardness A is 72 to 90. In this example, sidewall rubber is present as the fourth layer 24.

In this way, the first portion of the carcass folding end 6E is
Layer 21 and third layer 23 near the tire axial direction outer contour line o
By arranging the second layer 22 that is hard and relatively soft between them, the hard first layer 21 and the third layer 23 reduce the bending strain in the entire vicinity of the carcass folding end 6E, and particularly the first layer
The layer 21 reduces the shear strain between the steel cord / rubber portion by hardening its physical properties. Further, the relatively soft second layer 22 sandwiched between them absorbs the strain,
Distortion of the carcass folded end 6E is reduced.

Further, the thickness c of the first layer 21 on the perpendicular line M3 from the carcass folded end 6E to the contour line o of the outer surface.
1. In the thickness c2 of the second layer 22 and the thickness c3 of the third layer 23, 0.08 ≦ c1 / C ≦ 0.38, 0.04 ≦ c2 / C ≦ 0.20, 0.30 ≦ c3
/C≦0.75 and c2 ≦ c1 ≦ c3 are satisfied.

The shortest distance C can be set by the shortest distance A as described above, and usually the shortest distance C is about 5.0 to 15 mm from the value of the shortest distance A.

With this structure, the thickness and hardness of the carcass folded-back end 6E are well balanced, the deformation of the bead portion is suppressed, the durability thereof is improved, and the total thickness of the bead portion is reduced. It was found from the experiment that the weight of the tire can be reduced.

Further, it is preferable that the rubber physical properties of the respective layers have the following relations in order to produce the above effects. E * (MPa): second layer <first layer <third layer tan δ: second layer <third layer ≤ first layer Swell (%): third layer ≤ first layer ≤ second layer Hs: second Layer <1st layer <3rd layer

Where E * and tan δ are loss elastic moduli,
It represents the loss tangent, and both were measured with a Iwamoto Seisakusho Co., Ltd., under the conditions of room temperature 70 ° C, initial strain 10%, dynamic strain 2%, sample thickness 2.0 mm, length 30 mm, width 4.0 mm. It is a thing. Swell shows the degree of swelling, and is shown by the ratio of the weight after infiltration with toluene for 24 hours and that before infiltration. Hs is a numerical value of JISA hardness.

(Specific example) Tire size 11R 22.5
The tires shown in FIGS. 1, 2, 3, and 4 were prototyped according to the specifications of Tables 1 and 2 (Examples), and their performances were tested. A tire having a conventional structure (comparative example) was also tested to compare the performance.

Each test tire was mounted on an 8.25 × 22.5 rim, and an internal pressure of 800 kPa and a load of 2.0 times the standard maximum load were applied to the test tire at 20 km / min.
The running test was performed under the speed of h, and the time until peeling occurred at the outer end of the folded portion of the carcass was represented by an index with 100 being the example. The larger the value, the better.

As a result of the test, it was confirmed that the durability of the bead portion of the example was higher than that of the comparative example. Further, the rim assembly performance of each of the example products was better than that of the comparative example product.

[0038]

[Table 1]

[0039]

EFFECTS OF THE INVENTION The heavy duty pneumatic tire of the present invention, having the above-mentioned constitution, can prevent the peeling which tends to occur at the end of the carcass folded-back portion and enhance the durability of the bead portion.

[Brief description of drawings]

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

FIG. 2 is an enlarged sectional view showing a bead portion thereof.

FIG. 3 is an enlarged cross-sectional view showing the vicinity of a carcass folding end 6E of the bead portion.

FIG. 4 is a sectional view showing a conventional technique.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead part 5 bead core 6 carcass 6A carcass ply 6a Carcass body 6b Folding part 8 bead apex 9 Bead reinforcement layer 11 chafers 21 First Layer 22 Second layer 23 Third Layer

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 15 / 06,15 / 00,9 / 08

Claims (3)

(57) [Claims] 1. Tread portion (2) to sidewall portion (3)
Carcass consisting of a ply of a radial structure that is locked by folding back around the bead core (5) from the inner side in the tire axial direction to the outer side in the main body part that goes through to the bead core (5) of the bead part (4). 6), and a bead apex (8) arranged between the body portion 6a and the folded portion 6b of the carcass,
With a bead reinforcing layer (9) that uses a ply formed by arranging cords in parallel while passing outside in the tire axial direction of the folded-back portion 6b, and in a normal state in which it is fitted to the regular rim R and a regular internal pressure is applied, The edge 9E of the bead reinforcing layer (9) on the outer side in the tire axial direction is located radially inward of the carcass folding end 6E, and the edge of the bead reinforcing layer (9) on the inner side in the tire axial direction.
9F is the innermost end 5Q and the outermost end of the bead core (5) in the axial direction of the tire.
It is located inward in the radial direction of the straight line N connecting the 5Ps, and the distance h in the radial direction of the tire between the carcass turn-up end 6E and the edge 9E of the bead reinforcing layer (9) on the outer side in the tire axial direction is 5 mm or more and 20 mm. And the shortest distance A between the contour line o of the outer surface of the tire and the contour line i of the inner surface of the tire passing through the carcass folding end 6E, and the shortest distance B from the carcass folding end 6E to the carcass body 6a. , The ratio of the shortest distance C from the carcass folding end 6E to the outline o of the outer surface is 0.35 ≦ B / A ≦ 0.55, 0.25 ≦ C / A ≦ 0.40, and 1.00 ≦ B / C.
A heavy duty pneumatic tire characterized by a relationship of ≤1.80. 2. At least three rubber layers are arranged on a perpendicular line from the carcass folded-back end 6E to the contour line o of the outer surface of the tire, which is perpendicular to the contour line o. Pneumatic tires for heavy loads. 3. The three rubber layers are carcass folded-back ends 6E.
From the first layer (10), the second layer (11), and the third layer (12) arranged on the outer side in the tire axial direction toward the contour line o, and the thickness c1 of the first layer (10), In the thickness c2 of the second layer (11) and the thickness c3 of the third layer (12), 0.08 ≦ c1 / C ≦ 0.38, 0.04 ≦ c2 / C ≦ 0.2
The heavy duty pneumatic tire according to claim 2, wherein the pneumatic tire has a relationship of 0, 0.30 ≤ c3 / C ≤ 0.75, and c2 ≤ c1 ≤ c3.