JP2024058350A - Heavy duty pneumatic tires - Google Patents

Abstract

A heavy-duty pneumatic tire capable of improving the durability of a bead portion is provided.
[Solution] A heavy-duty pneumatic tire 1 has a carcass 6. The carcass 6 includes at least one carcass ply 6A. The carcass ply 6A includes a main body 6a and a turn-up portion 6b. The bead portion 4 is provided with a first reinforcing layer 9 extending from a first end 9a located on the inner side of the main body 6a in the tire axial direction to a second end 9b located on the outer side of the turn-up portion 6b in the tire axial direction, and a second reinforcing layer 10 at least a part of which is located on the outer side of the second end 9b in the tire axial direction. The first reinforcing layer 9 includes at least one steel ply 9A having a steel cord. The second reinforcing layer 10 includes at least one organic fiber ply 10A, 10B having an organic fiber cord. The first end 9a is located on the outer side of the second end 9b in the tire radial direction.
[Selected figure] Figure 2

Description

The present invention relates to a heavy-duty pneumatic tire having a carcass.

Various heavy-duty pneumatic tires with improved bead durability have been proposed. For example, the following Patent Document 1 proposes a heavy-duty pneumatic tire that has a first reinforcing layer made of a steel cord layer and a second reinforcing layer made of an organic fiber cord layer.

JP 2017-019452 A

However, the operating conditions required for heavy-duty pneumatic tires tend to become more severe every year, and the heavy-duty pneumatic tire of Patent Document 1 is also expected to have high durability in the bead portion under more severe conditions.

The present invention was devised in consideration of the above-mentioned circumstances, and its main objective is to provide a heavy-duty pneumatic tire that can improve the durability of the bead portion.

The present invention is a heavy-duty pneumatic tire having a carcass, the carcass including at least one carcass ply extending between a pair of bead portions, the carcass ply including a main portion extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a turn-up portion connected to the main portion and turning around the bead core from the inside to the outside in the tire axial direction, the bead portion including a first reinforcing layer extending from a first end located inside the main portion in the tire axial direction to a second end located outside the turn-up portion in the tire axial direction, and a second reinforcing layer at least a portion of which is located outside the second end in the tire axial direction, the first reinforcing layer including at least one steel ply having a steel cord, the second reinforcing layer including at least one organic fiber ply having an organic fiber cord, the first end being located radially outside the second end.

The heavy-duty pneumatic tire of the present invention has the above-mentioned configuration, which improves the durability of the bead portion.

1 is a cross-sectional view showing one embodiment of a heavy load pneumatic tire of the present invention. FIG.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
1 is a tire meridian cross-sectional view including a rotation axis showing a heavy-duty pneumatic tire (hereinafter sometimes simply referred to as "tire 1") according to this embodiment in a normal state. Here, the "normal state" refers to a state in which the tire 1 is mounted on a normal rim R, and the tire is adjusted to a normal internal pressure and is unloaded. Hereinafter, unless otherwise specified, the dimensions of each part of the tire 1 are values measured in this normal state.

A "genuine rim R" is a rim that is determined for each tire by a standard system that includes the standard on which tire 1 is based, for example, a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. If there is no standard system that includes the standard on which tire 1 is based, a "genuine rim R" is a rim that can be assembled and does not leak air, and that has the smallest rim diameter and the smallest rim width among all rims that can be assembled and do not leak air.

"Normal internal pressure" is the air pressure set for each tire by a standard system that includes the standard on which tire 1 is based, if there is such a system. For JATMA, it is the "maximum air pressure", for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is the "INFLATION PRESSURE". "Normal internal pressure" is the air pressure set for each tire by the manufacturer, etc., if there is no standard system that includes the standard on which tire 1 is based.

As shown in FIG. 1, the tire 1 of this embodiment includes a tread portion 2 having a ground contact surface 2a extending between a pair of tread ends Te, and a sidewall portion 3 extending radially inward from both axial sides of the tread portion 2. The tire 1 desirably further includes a bead portion 4 located radially inward of the sidewall portion 3. The bead portion 4 of this embodiment includes a bead core 5 extending in an annular shape. The bead core 5 is formed, for example, from a steel wire.

The tread end Te is the axially outermost contact point when the tire 1 is in a normal state and is loaded with a normal load and in contact with a flat surface with a camber angle of 0°. The tire equator C is the center position of the tread ends Te on both sides in the axial direction.

"Normal load" is the load determined for each tire by a standard system that includes the standard on which tire 1 is based, if there is such a system. For JATMA, it is the "maximum load capacity." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "LOAD CAPACITY." If there is no standard system that includes the standard on which tire 1 is based, "normal load" is the load determined for each tire by the manufacturer, etc.

The tire 1 of this embodiment has a carcass 6 that extends from the tread portion 2 through a pair of sidewall portions 3 to a pair of bead portions 4, and a belt layer 7 that is disposed radially outward of the carcass 6 in the tread portion 2. The belt layer 7 includes at least one, for example, four belt plies 7A to 7D.

The carcass 6 includes at least one carcass ply 6A, one in this embodiment, that extends between a pair of bead portions 4. The carcass ply 6A in this embodiment includes a main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a folded-back portion 6b that is connected to the main body portion 6a and folds back around the bead core 5 from the inside to the outside in the tire axial direction.

Figure 2 is an enlarged cross-sectional view of the bead portion 4. As shown in Figure 2, the bead portion 4 is preferably provided with a bead apex rubber 8 that extends tapered from the bead core 5 toward the outside in the tire radial direction. The bead portion 4 of this embodiment is further provided with a first reinforcing layer 9 arranged adjacent to the carcass ply 6A around the bead core 5, and a second reinforcing layer 10, at least a portion of which is located outside the first reinforcing layer 9 in the tire axial direction. Such a bead portion 4 has high rigidity and can suppress deformation toward the outside in the tire axial direction with the bead core 5 as a fulcrum, thereby improving durability.

The first reinforcing layer 9 includes at least one steel ply 9A having a steel cord, in this embodiment one steel ply 9A. The second reinforcing layer 10 includes at least one organic fiber ply 10A, 10B having an organic fiber cord, in this embodiment two organic fiber plies 10A, 10B. Such a bead portion 4 helps to improve durability due to the high rigidity provided by the first reinforcing layer 9 and the effect of the second reinforcing layer 10 in suppressing deformation outward in the tire axial direction.

The first reinforcing layer 9 in this embodiment extends from a first end 9a located on the inside in the tire axial direction of the main body portion 6a of the carcass ply 6A to a second end 9b located on the outside in the tire axial direction of the folded-back portion 6b. It is desirable that at least a portion of the second reinforcing layer 10 is located on the outside in the tire axial direction of the second end 9b of the first reinforcing layer 9. In such a bead portion 4, the second end 9b, where stress is likely to concentrate in the first reinforcing layer 9, can be reinforced by the second reinforcing layer 10, thereby improving durability.

The first end 9a of the first reinforcing layer 9 of this embodiment is located radially outward of the second end 9b. Such a first reinforcing layer 9 can more effectively suppress deformation outward in the tire axial direction with the bead core 5 as a fulcrum. Therefore, the tire 1 of this embodiment can improve the durability of the bead portion 4.

In a more preferred embodiment, the height h1 from the bead base line BL to the first end 9a is 1.2 to 2.2 times the height h2 from the bead base line BL to the second end 9b. By making the height h1 1.2 times or more the height h2, it is possible to reliably suppress deformation outward in the tire axial direction with the bead core 5 as a fulcrum. By making the height h1 2.2 times or less the height h2, it is possible to suppress the first reinforcing layer 9 from becoming excessively large, suppressing an increase in weight, and increasing rigidity.

In this embodiment, the bead portion 4 is provided with a chafer rubber 11 that defines the outer surface 4a of the bead portion 4. At least a portion of the chafer rubber 11 in this embodiment is located outside the second reinforcing layer 10 in the tire axial direction. Such a bead portion 4 can reduce external forces acting on the second reinforcing layer 10 due to the cushioning function of the chafer rubber 11, and as a result, the durability can be improved by suppressing deformation and damage to the second reinforcing layer 10.

It is desirable for the chafer rubber 11 to have a recess 11a in which the outer surface 4a on the outside of the tire in the axial direction is partially recessed inward in the tire axial direction. Such a recess 11a can reduce the amount of deformation of the bead portion 4 outward in the tire axial direction when a load is applied, and can improve the durability of the bead portion 4.

The thickness t1 of the chafer rubber 11 at the position having the recess 11a is preferably 5 mm or more. Here, the position having the recess 11a is the position of the recess 11a that is the most recessed. If the position of the most recessed has a certain length, it is the center position of that length. Furthermore, the thickness t1 of the chafer rubber 11 at the position having the recess 11a is the shortest distance between the outer surface 4a at the position having the recess 11a and the outer surface of the second reinforcing layer 10. By making the thickness t1 5 mm or more, the cushioning function of the chafer rubber 11 can be reliably exerted.

It is desirable that the radially outer end 11b of the chafer rubber 11 is located radially outboard of the radially outer ends 10a, 10b of at least one of the two organic fiber plies 10A, 10B. Such a chafer rubber 11 can suppress damage originating from the radially outer ends 10a, 10b of at least one of the two organic fiber plies 10A, 10B, and can improve the durability of the bead portion 4.

In this embodiment, the radially outer end 11b of the chafer rubber 11 is located radially outboard of the radially outer ends 10a, 10b of both organic fiber plies 10A, 10B. Such a chafer rubber 11 can suppress damage originating from the respective outer ends 10a, 10b of the two organic fiber plies 10A, 10B, and can more reliably improve the durability of the bead portion 4.

In this embodiment, the two organic fiber plies 10A, 10B of the second reinforcing layer 10 have organic fiber cords that cross each other. Such a second reinforcing layer 10 has high rigidity, which suppresses deformation and reduces distortion, thereby improving the durability of the bead portion 4.

The organic fiber cord is, for example, a nylon cord. Such an organic fiber cord has excellent cost performance and helps to achieve excellent durability of the bead portion 4 at a low price. Note that the organic fiber cord is not limited to such a nylon cord, and various cords such as polyester cord, aramid cord, vinylon cord, etc. may be used as appropriate.

In this embodiment, the radially outer end 8a of the bead apex rubber 8 is located radially outward of the radially outer end 6c of the turned-up portion 6b of the carcass ply 6A. Such a bead apex rubber 8 can improve the rigidity of the bead portion 4, which helps to improve the durability of the bead portion 4.

The thickness t2 of the bead apex rubber 8 at the outer end 6c of the turn-up portion 6b is preferably 0.6 to 0.9 times the maximum width w1 of the bead core 5. Here, the thickness t2 of the bead apex rubber 8 at the outer end 6c of the turn-up portion 6b corresponds to the length of the bead apex rubber 8 on a perpendicular line drawn from the outer end 6c of the turn-up portion 6b to the main body portion 6a.

By making the thickness t2 0.6 times or more the maximum width w1, the rigidity near the outer end 6c of the folded portion 6b can be improved. By making the thickness t2 0.9 times or less the maximum width w1, the main body 6a and the folded portion 6b of the carcass 6 are prevented from being separated excessively, which helps maintain the high rigidity of the bead portion 4.

The bead apex rubber 8 includes, for example, a first apex 8A extending from the bead core 5 and a second apex 8B arranged radially outward of the first apex 8A. Such a bead apex rubber 8 can reinforce the bead portion 4 with different types of rubber, which helps to improve the durability of the bead portion 4.

The complex elastic modulus of the first apex 8A is preferably 50 MPa or more. Here, the complex elastic modulus is a value measured using a dynamic viscoelasticity measuring device under the following conditions in accordance with the provisions of JIS-K6394.
Initial distortion: 10%
Dynamic strain amplitude: ±1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70°C

By having the complex elastic modulus of the first apex 8A bead portion 4 bead rigidity is improved, and deformation outward in the tire axial direction can be suppressed, improving the durability of the bead portion 4.

It is desirable that the complex modulus of elasticity of the second apex 8B is smaller than the complex modulus of elasticity of the first apex 8A. Such a bead apex rubber 8 can effectively suppress damage to the bead portion 4 by alleviating the shear stress acting on the folded portion 6b of the carcass ply 6A through the low-elasticity second apex 8B.

In this embodiment, the outer end 8b of the first apex 8A of the bead apex rubber 8 is located radially outward of the radially outer end 6c of the turned-up portion 6b of the carcass ply 6A. Such a bead apex rubber 8 can further improve the rigidity near the outer end 6c of the turned-up portion 6b, thereby improving the durability of the bead portion 4.

The above describes in detail a particularly preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment and can be modified in various ways.

[Additional Notes]
The present invention is as follows.

[Invention 1]
A heavy-duty pneumatic tire having a carcass,
The carcass includes at least one carcass ply extending between a pair of bead portions,
The carcass ply includes a main body portion extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a turn-up portion continuing to the main body portion and turning back around the bead core from the inside to the outside in the tire axial direction,
The bead portion is provided with a first reinforcing layer extending from a first end located on the inner side of the main body portion in the tire axial direction to a second end located on the outer side of the turned-up portion in the tire axial direction, and a second reinforcing layer having at least a portion located on the outer side of the second end in the tire axial direction,
The first reinforcing layer includes at least one steel ply having a steel cord;
The second reinforcing layer includes at least one organic fiber ply having an organic fiber cord,
The first end is located outward in a tire radial direction from the second end.
Heavy duty pneumatic tires.

[Invention 2]
The bead portion is provided with a chafer rubber, at least a portion of which is located outside the second reinforcing layer in the tire axial direction and which defines an outer surface of the bead portion,
The heavy-duty pneumatic tire according to claim 1, wherein the chafer rubber has a recess in which the outer surface on the outer side in the tire axial direction is partially recessed inward in the tire axial direction.

[The present invention 3]
3. The heavy-duty pneumatic tire according to claim 2, wherein the thickness of the chafer rubber at a position having the recess is 5 mm or more.

[Invention 4]
The second reinforcing layer includes two of the organic fiber plies,
The heavy-duty pneumatic tire according to the second or third aspect of the present invention, wherein an outer end in the tire radial direction of the chafer rubber is located radially outward of an outer end in the tire radial direction of at least one of the two organic fiber plies.

[Invention 5]
The heavy-duty pneumatic tire according to the fourth aspect of the present invention, wherein an outer end in the tire radial direction of the chafer rubber is positioned radially outward of both outer ends in the tire radial direction of the two organic fiber plies.

[Invention 6]
6. The heavy-duty pneumatic tire according to claim 4 or 5, wherein the organic fiber cords of the two organic fiber plies cross each other.

[Invention 7]
7. The heavy-duty pneumatic tire according to any one of claims 1 to 6, wherein the height from the bead base line to the first end is 1.2 to 2.2 times the height from the bead base line to the second end.

[The present invention 8]
The bead portion is provided with a bead apex rubber that extends in a tapered shape from the bead core toward an outer side in a tire radial direction,
8. The heavy-duty pneumatic tire according to any one of claims 1 to 7, wherein the bead apex rubber includes a first apex having a complex elastic modulus of 50 MPa or more.

[The present invention 9]
an outer end of the bead apex rubber in a radial direction of the tire is located radially outward of an outer end of the turned-up portion in a radial direction of the tire;
9. The heavy-duty pneumatic tire according to claim 8, wherein the thickness of the bead apex rubber at the position of the outer end of the turned-up portion is 0.6 to 0.9 times the maximum width of the bead core.

[Invention 10]
10. The heavy-duty pneumatic tire according to any one of claims 1 to 9, wherein the organic fiber cord is a nylon cord.

Reference Signs List 1 Heavy-duty pneumatic tire 6 Carcass 6A Carcass ply 6a Main body portion 6b Turn-up portion 9 First reinforcing layer 9A Steel ply 9a First end 9b Second end 10 Second reinforcing layer 10A Organic fiber ply 10B Organic fiber ply

Claims (10)

A heavy-duty pneumatic tire having a carcass,
The carcass includes at least one carcass ply extending between a pair of bead portions,
The carcass ply includes a main body portion extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a turn-up portion continuing to the main body portion and turning back around the bead core from the inside to the outside in the tire axial direction,
The bead portion is provided with a first reinforcing layer extending from a first end located on the inside in the tire axial direction of the main body portion to a second end located on the outside in the tire axial direction of the turned-up portion, and a second reinforcing layer at least a portion of which is located on the outside in the tire axial direction of the second end,
The first reinforcing layer includes at least one steel ply having a steel cord;
The second reinforcing layer includes at least one organic fiber ply having an organic fiber cord,
The first end is located outward in a tire radial direction from the second end.
Heavy duty pneumatic tires. The bead portion is provided with a chafer rubber, at least a portion of which is located outside the second reinforcing layer in the tire axial direction and which defines an outer surface of the bead portion,
The heavy-duty pneumatic tire according to claim 1 , wherein the chafer rubber has a recess in which the outer surface on an outer side in the tire axial direction is partially recessed inward in the tire axial direction. The heavy-duty pneumatic tire according to claim 2, wherein the thickness of the chafer rubber at the location having the recess is 5 mm or more. The second reinforcing layer includes two of the organic fiber plies,
4. The heavy-duty pneumatic tire according to claim 2, wherein a radially outer end of the chafer rubber is positioned radially outward of a radially outer end of at least one of the two organic fiber plies. The heavy-duty pneumatic tire according to claim 4, wherein the radially outer end of the chafer rubber is located radially outward of both radially outer ends of the two organic fiber plies. The heavy-duty pneumatic tire according to claim 4, wherein the organic fiber cords of the two organic fiber plies cross each other. The heavy-duty pneumatic tire according to any one of claims 1 to 3, wherein the height from the bead base line to the first end is 1.2 to 2.2 times the height from the bead base line to the second end. The bead portion is provided with a bead apex rubber that extends in a tapered shape from the bead core toward an outer side in a tire radial direction,
4. The heavy duty pneumatic tire according to claim 1, wherein the bead apex rubber includes a first apex having a complex elastic modulus of 50 MPa or more. an outer end of the bead apex rubber in a radial direction of the tire is located radially outward of an outer end of the turned-up portion in a radial direction of the tire;
9. The heavy-duty pneumatic tire according to claim 8, wherein a thickness of the bead apex rubber at an outer end of the turned-up portion is 0.6 to 0.9 times a maximum width of the bead core. The heavy-duty pneumatic tire according to any one of claims 1 to 3, wherein the organic fiber cord is a nylon cord.

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