JPH11115412A - Pneumatic radial tire for heavy duty - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for heavy load having good cut- resistance and wear-resistance and mainly used for the rough ground. SOLUTION: A belt 2 is arranged inside in a radial direction and includes two inside belt layers 21, 22 made of coating rubber, in which a substantially non-elongating metallic code is buried, and two outside belt layers 23, 24. The inside belt layers 21, 22 are laminated such that the codes extend in parallel to each other and cross each other between the neighboring layers at the code angle α of 0 to 15 degrees to a peripheral direction, and a code angle β to the peripheral direction is 10 to 40 degrees, and the cross-sectional width of the inside belt layer is 20 to 60% of the width of a tread contacting the ground when a normal load is statically applied to the tire. The outside belt layer has a cross-sectional width of 100 to 450% of the cross-sectional width of the inside belt layer and is divided into right and left sides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a bead core provided on a pair of right and left bead portions and extending from one bead portion to the other bead portion. A carcass ply composed of a radial cord layer wound around the bead portion and a belt and a tread arranged radially outside the crown portion of the carcass ply, and mainly used for traveling on rough terrain. The present invention relates to a pneumatic radial tire for heavy loads.

[0002]

2. Description of the Related Art In general, heavy-duty pneumatic tires such as pneumatic tires for construction vehicles are often used on rough roads or rough terrain where rocks and crushed stones are scattered. Failure easily occurs. In order to suppress or prevent the separation failure at the end of the belt, a narrow belt layer having a small cord angle with respect to the circumferential direction is disposed inside the conventional belt, that is, between the belt and the carcass, and the internal pressure is applied to the tire. It has been proposed to increase the cord angle with respect to the circumferential direction of the conventional belt by maintaining the cross-section of the tire in a desired shape by suppressing the tension when the tire is filled, suppressing the radial growth.

[0003]

However, when a narrow belt layer in which the cord arrangement angle with respect to the circumferential direction is reduced as described above is arranged between the belt and the carcass,
The rigidity at the center of the tire is significantly increased, so that when the tire steps on a projection such as a rock or a crushed stone, the envelope power characteristic surrounding the projection is reduced, and the cut-penetration resistance of the tire is reduced. Further, when the rigidity at the center of the tire becomes extremely high, a step occurs in the rigidity distribution in the width direction of the tread, and the contact pressure distribution at the time of contact with the ground tends to be nonuniform, so that the wear resistance of the tread tends to decrease.

It is an object of the present invention to provide a heavy-duty pneumatic radial tire for traveling on rough terrain, which eliminates the above-mentioned drawbacks of conventional tires and has excellent cut-through resistance and wear resistance. is there.

[0005]

In order to achieve the above object, a tire according to the present invention comprises a bead core provided on a pair of left and right bead portions, and a tire extending from one bead portion to the other bead portion. Pneumatically provided with a carcass ply composed of a radial cord layer wound around the bead core and moored at a bead portion, and a belt and a tread disposed radially outside a crown portion of the carcass ply in a radial direction. In a radial tire, the belt comprises: (1) at least two inner belt layers disposed radially inward and having a substantially inextensible metal cord embedded in a covering rubber; And at least two outer belt layers having a substantially inextensible metal cord embedded in the coated rubber; and (2) the inner belt layer having a core (3) the outer belt layer is formed such that the cord angle α with respect to the circumferential direction is larger than 0 degree and equal to or smaller than 15 degrees so that the cords intersect each other between adjacent layers. The cord angle β with respect to the circumferential direction is 10 so that the cords extend parallel to each other in the layer, and the cords intersect each other between the adjacent layers.
(4) The inner belt layer has a cross-sectional width that is equal to a normal internal pressure by assembling the tire with a regular rim, 20 to 60% of the tread contact width when a normal load is statically applied, and (5) the outer belt layer has:
A pneumatic radial for heavy loads mainly used on rough terrain, having a cross-sectional width of 100 to 450% of the cross-sectional width of the inner belt layer and being divided into right and left sides with respect to the equator line of the tire. Tires.

In order to achieve the above object, in the tire according to the present invention, the tire covers both ends of the outer belt layer.
At least one protective belt layer, which is formed by embedding a substantially extensible metal cord in the covering rubber and having a width larger than the cross-sectional width of the outer belt layer, is disposed radially outside the outer belt layer. Is preferred.

[0007] In order to achieve the above object, in the tire according to the present invention, the outer belt layer comprises at least two rubber-coated cord layers having different cross-sectional widths, and the cord angle of the layer having the larger cross-sectional width is smaller than the cross-sectional width. Preferably, it is greater than the cord angle of the small layer.

[0008] Pneumatic tires are available in JATMA (Japan), TRA (US) and ET, depending on their size.
It is used by being mounted on a standard rim specified in a standard issued by RTO (Europe) or the like, and this standard rim is usually called a regular rim. In this specification, the "regular rim" refers to a standard rim in an application size specified in the 1997 edition of YEAR BOOK issued by the United States Tire and Rim Association TRA. Similarly, "regular load" refers to the 1999 tire and rim association TRA issued by the TRA.
Applicable size specified in the 7-year version of YEAR BOOK
The "normal internal pressure" refers to the maximum load at the ply rating and the air pressure corresponding to the maximum load at the applicable size ply rating specified in the 1997 edition of YEAR BOOK issued by the American Tire and Rim Association TRA. In the present specification, the “substantially non-extensible metal cord” means that the elongation at break (Eb) is 1 to 3
% Metal cord, preferably steel cord
"Substantially extensible metal cord" refers to a metal cord, preferably a steel cord, having an elongation at break (Eb) of 4 to 7%, and the "cross-sectional width of the belt layer" refers to the rotational axis of the tire. Refers to the width of the belt layer in the cross section including.

[0009] The tire of the present invention has the above-described structure. In particular, (1) the belt is disposed at least radially inward and having a substantially inextensible metal cord embedded in a covering rubber. (2) an inner belt layer, comprising: two inner belt layers; and at least two outer belt layers disposed radially outward and having a substantially inextensible metal cord embedded in the coated rubber. (3) is formed by stacking so that the cord angle α with respect to the circumferential direction is larger than 0 degree and equal to or smaller than 15 degrees so that the cords extend in parallel in the layers and the cords cross each other between the adjacent layers. The outer belt layer has a cord angle β with respect to the circumferential direction of 10 to 40 degrees and a cord angle α of the inner belt layer such that the cords extend parallel to each other within the layer and the cords intersect each other between adjacent layers. Formed by laminating so as to hear,
(4) The cross-sectional width of the inner belt layer is 20 to 60% of the tread contact width when the tire is rim-assembled into a regular rim, filled with a regular internal pressure, and a regular load is statically applied. The layer has a cross-sectional width of 100 to 4 of the inner belt layer.
A pneumatic radial tire for heavy-duty use mainly for traveling on rough terrain, having a cross-sectional width of 50% and being divided into right and left sides with respect to the equator line of the tire, having excellent cut-through resistance and wear resistance. . In other words, the inner belt layer having a small cord angle with respect to the circumferential direction (0 ° <α ≦ 15 °) and a narrow width (20 to 60% of the tread contact width) bears the tension when the tire is filled with the internal pressure, The outer belt layer increases the cord angle (α <β, 10 ≦ β) because the cross section of the tire is maintained in a desired shape and the diameter growth is suppressed.
≦ 40), and the separation failure at the belt end is suppressed or prevented. Moreover, since the outer belt layer is divided into right and left sides with respect to the equator line of the tire, the rigidity at the center of the tire is reduced, and the tension of the entire belt becomes uniform. Lowering the tension at the center of the tire, that is, lowering the stiffness, improves the envelope power characteristics that wrap the protrusion when the tire steps on a protrusion such as rock or crushed stone, and cuts the tire. The penetration characteristics are excellent. In addition, the tension of the entire belt becomes uniform, that is, the rigidity distribution becomes uniform, so that the wear resistance of the tread is improved.

[0010] In order to further improve the cut-through resistance, the tire of the present invention, as described above, extends substantially wider than the cross-sectional width of the outer belt layer so as to cover both ends of the outer belt layer. It is preferable that at least one protective belt layer formed by embedding a metallic cord in the covering rubber is disposed radially outside the outer belt layer.

In order to effectively suppress or prevent separation failure at the end of the belt, in the tire according to the present invention, the outer belt layer comprises at least two rubber-coated cord layers having different cross-sectional widths, and has a large cross-sectional width. It is preferable that the cord angle of the layer is larger than the cord angle of the layer having a small sectional width.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic radial tire for a construction vehicle according to an embodiment of the present invention and a pneumatic radial tire for a construction vehicle according to a comparative example will be described below with reference to the drawings. The tire size is 40.
00R57.

FIG. 1 is a schematic sectional view showing an arrangement of a belt layer of a pneumatic radial tire for construction vehicles according to an embodiment of the present invention. The tire according to the first embodiment shown in FIG. 1 has a bead core (not shown) provided on a pair of right and left beads, extends from one bead to the other bead, and is wound around the bead core. Carcass ply 1 consisting of a radial cord layer
And a pneumatic radial tire for construction vehicles comprising a belt 2 and a tread 3 arranged radially outward of a crown portion of a carcass ply. The belt 2 is disposed radially inward, and has two inner belt layers 21 and 22 formed by embedding a substantially inextensible steel cord having an elongation at break (Eb) of 2% in a covering rubber. And a two-layered steel cord which is disposed radially outside the inner belt layers 21 and 22 and has an elongation at break (Eb) of 2% and is substantially inextensible. The outer belt layers 23 and 24 are disposed radially outside the outer belt layers 23 and 24, and the elongation at break (Eb) is 6%.
And a protective belt layer 25, 26 comprising a substantially extensible steel cord embedded in a covering rubber. The inner belt layers 21 and 22 have a cord angle α1 with respect to the circumferential direction of the inner belt layer 21 of 7 degrees ascending to the left so that the cords extend parallel to each other in the layers and the cords cross each other between adjacent layers. Belt layer 22
Are stacked at an angle of 8 degrees which rises to the right with respect to the circumferential direction. The outer belt layers 23 and 24 are formed such that the cord angle β1 with respect to the circumferential direction of the outer belt layer 23 rises to the left by 30 degrees so that the cords extend parallel to each other in the layers and the cords cross each other between adjacent layers. Layer 2
4 are laminated at a cord angle β2 with respect to the circumferential direction which rises to the right to 20 degrees. The cord angles β (β1, β2) with respect to these circumferential directions are larger than the cord angles α (α1, α2). The cross-sectional widths of the inner belt layers 21 and 22 are 320 mm and 280 mm, respectively. When the tire is assembled on a regular rim, the regular internal pressure is filled, and the regular load is statically applied, the tread contact width is 940 mm. Therefore, the cross-sectional widths of the inner belt layers 21 and 22 are 34% and 30% of the tread contact width, respectively.
It is. The size of the tire of this embodiment is 40.00.
Since it is R57, the regular rim is 29.00 / 6.0,
The regular internal pressure is 700kPa and the regular load is 60000kg
It is. The cross-sectional widths from the right end to the left end of the outer belt layers 23 and 24 are 710 mm and 610 mm, respectively. , 350mm
And 280 mm. The outer belt layers 23 and 24 have a cross-sectional width of 191 to 254% of the cross-sectional width of the inner belt layers 21 and 22. The cross-sectional widths of the protective belt layers 25 and 26 are 840 mm and 700 mm, respectively. In the outer belt layers 23, 24, the cord angle β1 = 30 ° of the layer 23 having a large sectional width is larger than the cord angle β2 = 20 ° of the layer 24 having a small sectional width.

The pneumatic radial tire for a construction vehicle of the comparative example is the same as the tire of the above embodiment except that the outer belt layers 23 and 24 are not divided into right and left sides with respect to the equator line of the tire.

The pneumatic radial tire for a construction vehicle of the above embodiment and the pneumatic radial tire for a construction vehicle of the above comparative example.
For tires, a comparative test of cut-penetration resistance and wear resistance was performed.

In the comparative test of the cut penetration resistance, each test tire was assembled on a regular rim (29.00 / 6.0) with a regular internal pressure (700 kPa) and the tip was 100 m in diameter.
A plunger test to check the strength of the tire by pressing the hemispherical protrusion of m to the center of the tread to break the tire and calculate and evaluate the breaking energy from the load at the time of breaking and the depth at which the protrusion bites into the tire Things. As a result of the comparative test, when the tire of the comparative example was set to 100, the tire of the example was 120.

In the comparative test of the abrasion resistance characteristics, each of the test tires was put on a regular rim (29.00 / 6.0) at a regular internal pressure (7.
The rim is assembled at 00 kPa), a load of 72 tons is applied, and the wear amount of the tread after running for a certain period of time is measured and compared with an indoor drum tester in which the surface roughness of the drum is increased. As a result of the comparative test, assuming that the tire of the comparative example is 100, the tire of the above example was 107.

[0018]

From the results of the above comparative tests, it is understood that the present invention can provide a pneumatic radial tire for heavy load excellent in cut-through resistance and abrasion resistance.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an arrangement of a belt layer of a tire according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 carcass 2 belt 3 tread 21 first belt layer (inner belt layer) 22 second belt layer (inner belt layer) 23 third belt layer (outer belt layer) 24 fourth belt layer (outer belt layer) 25 fifth belt Layer (Protective Belt Layer) 26 6th Belt Layer (Protective Belt Layer)

Claims (3)

[Claims] 1. A bead core provided on a pair of left and right bead portions, and a radial cord extending from one bead portion to the other bead portion, wound around the bead core and moored to the bead portion. Carcass ply consisting of layers,
A pneumatic radial tire having a belt and a tread radially outwardly disposed on a crown portion of the carcass ply, wherein: (1) the belt is radially inwardly disposed and substantially inextensible metal; At least two inner belt layers having a cord embedded in a covering rubber;
At least two outer belt layers disposed radially outward and having a substantially inextensible metal cord embedded in a covering rubber; and (2) the inner belt layer includes a cord within the layer. The cord angle α with respect to the circumferential direction extends parallel to each other, and the cords intersect each other between adjacent layers.
(3) The outer belt layer has a circumferential direction such that the cords extend parallel to each other within the layer and the cords intersect each other between adjacent layers. (4) The inner belt layer has a cross-sectional width of 10 to 40 degrees and greater than the cord angle α of the inner belt layer.
The tire is rim-assembled into a regular rim, filled with a regular internal pressure, and has a tread contact width of 20 to 60% when a regular load is statically applied. (5) The outer belt layer is formed of the inner belt layer. A pneumatic radial tire for heavy load mainly used on rough terrain, having a cross-sectional width of 100 to 450% of the cross-sectional width and being divided right and left with an equatorial line of the tire interposed therebetween. 2. A method for covering both ends of the outer belt layer,
At least one protective belt layer, which is formed by embedding a substantially extensible metal cord in the covering rubber and having a width larger than the cross-sectional width of the outer belt layer, is disposed radially outside the outer belt layer. The pneumatic tire according to claim 1, wherein: 3. The outer belt layer comprises at least two rubber-coated cord layers having different cross-sectional widths, wherein a cord angle of a layer having a large cross-section is larger than a cord angle of a layer having a small cross-section width. Item 3. The pneumatic tire according to Item 1 or 2.