JP2007045334A - Flat pneumatic radial tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat pneumatic radial tire for heavy load capable of considerably enhancing the durability and the uneven wear resistance of the tire. <P>SOLUTION: In the flat pneumatic radial tire for heavy load in which a steel cord belt layer 6 having a plurality of plies is arranged on the outer circumference of a carcass layer 4, the steel cord belt layer 6 comprises a 0°-belt layer 7 of at least one ply which is arranged immediately on the carcass layer 4 while the cord angle with respect to the tire circumferential direction is substantially 0°, and bias belt layers 8 of at least two plies which is arranged on the outer circumferential side of the 0° belt layer 7 while the cord angle with respect to the tire circumferential direction is substantially equal to an equilibrium angle within a range of 45-65°. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heavy load flat pneumatic radial tire, and more particularly to a heavy load flat pneumatic radial tire that further improves the durability and uneven wear resistance of the tire.

  In recent years, flattening is progressing not only in pneumatic radial tires for passenger cars but also in pneumatic radial tires for heavy loads, and super-flat tires with a flatness ratio of 60% or less are increasing. In the Japanese market, it is starting to spread especially with low-floor buses. In such a super flat radial tire, since the tread is wide, how to uniformly ground the wide tread with respect to the road surface is an important issue. That is, if the grounding property is not uniform, there is a problem that the durability and uneven wear resistance of the tire deteriorate.

  The ground contact shape of the heavy-duty pneumatic radial tire depends on the configuration of the belt layer embedded in the tread. In a conventional general radial tire, the cord angle with respect to the tire circumferential direction of the steel cord in the belt layer is set to a bias of about 15 to 60 degrees, and the cord directions are arranged to cross each other. However, if the belt layer configuration having such a bias structure is used for a flat radial tire as it is, the width of the belt layer in the flat radial tire is wide, so that the circumferential rigidity is reduced at the edge of the belt layer. The shoulder edge portion is extremely swollen like the ground contact shape shown in FIG. Further, since the interlaminar shear force at the edge portion of the belt layer becomes large, a peeling failure occurs at the edge portion. Therefore, the tire causes uneven wear and decreases durability.

  Conventionally, as a countermeasure against the problems that occur in the flat radial tire as described above, a so-called 0 degree belt layer in which steel cords are arranged at substantially 0 degree with respect to the tire circumferential direction is inserted into the bias belt layer. Proposals have been made to increase the directional rigidity (Patent Document 1, etc.). For example, in Patent Document 1, a 0-degree belt layer having a narrower width than the bias belt layer is inserted between two bias belt layers in which a steel cord has a cord angle of 10 to 45 degrees with respect to the tire circumferential direction. At the same time, a thin rubber layer is interposed between the end portions of the bias belt layer so as to be bonded.

Thus, by inserting the 0 degree belt layer into the bias belt layer, the effect of improving the durability and uneven wear resistance of the tire is recognized as compared with the conventional tire in which only the bias belt layer is arranged. However, the obtained durability and uneven wear resistance effects do not always reach a satisfactory level, and at present, further improvement is required.
JP 2001-522748 A

  An object of the present invention is to provide a heavy-duty flat pneumatic radial tire that further improves the durability and uneven wear resistance of the tire.

  The heavy-duty flat pneumatic tire of the present invention is a heavy-duty flat pneumatic radial tire in which a plurality of ply steel cord belt layers are arranged on the outer periphery of the carth layer, and the steel cord belt layer is arranged immediately above the carcass layer. And at least one ply of 0 degree belt layer having a cord angle with respect to the tire circumferential direction of substantially 0 degrees, and a cord angle with respect to the tire circumferential direction of 45 to 65 degrees. And a bias belt layer of at least two plies having a substantial equilibrium angle in the range of

  According to the present invention, a steel cord belt is arranged such that a 0-degree belt layer having a cord angle of substantially 0 degrees is disposed immediately above the carcass layer, and a bias belt layer having a cord angle of substantially equilibrium angle is disposed thereon. Since the 0-degree belt layer is provided with high rigidity in the tire circumferential direction, the rigidity of the entire tread is equalized, and the bias belt layer has a cord angle with respect to the mechanical strength of the cord-reinforced composite material. By setting the equilibrium angle (= 54.7 degrees) or in the vicinity thereof, the deformation of the tire circumferential direction tension is substantially prevented from occurring according to the theory of the equilibrium angle. This makes it difficult for shear deformation to occur between the layer and the bias belt layer. Therefore, the durability and uneven wear resistance of the tire can be further improved by the synergistic action of the 0 degree belt layer and the bias belt layer.

FIG. 1 is a diagram illustrating a meridional section of a heavy-duty flat pneumatic radial tire according to the present invention, and FIG. 2 is a partial development view of a steel cord belt layer of the tire as viewed from the outside in the radial direction.
1 and 2, 1 is a tread portion, 2 is a sidewall portion, 3 is a bead portion, and 4 is a carcass layer. The carcass layer 4 is configured such that a large number of steel cords 4a are arranged at 90 degrees with respect to the tire circumferential direction, and the bead portions 3, 3 are respectively passed from the central tread portion 1 through the left and right sidewall portions 2, 2. 3, both end portions thereof are folded around the bead cores 5 and 5 from the tire inner side to the outer side.

  In the tread portion 1, a steel belt layer 6 made of a plurality of plies is disposed on the outer peripheral side of the carcass layer 4. In the embodiment, the steel belt layer 6 is formed by laminating a 0-degree belt layer 7 made of 2 plies, a bias belt layer 8 made of 2 plies, and a protective belt layer 9 of 1 ply in order from right above the carcass layer 4 to the outside. It is configured. Thus, among the belt layers constituting the steel belt layer 6, the 0 ° belt layer 7 has the widest width Wo, which is 75 to 85% of the total tire width W. The width of the bias belt layer 8 is next to the 0 degree belt layer 7 and the width Wb is 60 to 80% of the total tire width W. The protective belt layer 9 is the narrowest and its width Wp is 25 to 70% of the total tire width W.

  The innermost 0-degree belt layer 7 is formed by winding a steel cord 7a immediately above the carcass layer 4 in parallel with a cord angle of substantially 0 degrees with respect to the tire circumferential direction. The 0-degree belt layer 7 is formed by winding a rubberized tape made of one or 2 to 10 steel cords 7a continuously and spirally in the tire circumferential direction. In this way, the 0 degree belt layer 7 in which the steel cords 7a are arranged at an angle of about 0 degrees with respect to the tire circumferential direction provides a high rigidity in the tire circumferential direction and equalizes the tread rigidity as a whole. As shown by the broken line B in FIG.

  The 0-degree belt layer 7 may be provided with at least one ply, but preferably two plies or more are provided as in the illustrated example. By providing two or more plies of the 0-degree belt layer 7, the tension of the steel cord 7a can be equalized over the entire area, and the uniform grounding shape can be made more advantageous. The upper limit of the number of plies of the 0-degree belt layer 7 is not particularly limited, but is preferably set to 1 or 2 plies from the viewpoint of suppressing weight.

  In the 0 degree belt layer 7, the cord angle is substantially 0 degree with respect to the tire circumferential direction. In addition to the case where the cord angle of the steel cord 7a is completely 0 degree, the cord angle is within a range of 0 degree ± 3 degrees. It means to include.

  The steel cord used for the 0 degree belt layer 7 is different from the steel cord used for the bias belt layer 8 and the protective belt layer 9. For the bias belt layer 8 and the protective belt layer 9, steel cords having a linear stress-strain relationship are used. For the 0 ° belt layer 7, steel cords having nonlinear properties are used. Non-linear characteristics are those in which the strain change (elongation) is large up to about 3% in the low stress region of the stress-strain relationship and the strain change (elongation) is small in the middle and high stress regions. Say. By using a steel cord having non-linear characteristics in the 0 degree belt layer in this way, a lift during vulcanization can be made smooth and a tire excellent in uniformity can be obtained.

  The bias belt layer 8 disposed on the outer peripheral side of the 0 degree belt layer 7 is formed such that the steel cords 8a are arranged in parallel at a cord angle α of 45 to 65 degrees with respect to the tire circumferential direction. As the bias belt layer 8, at least two plies are disposed, and preferably, the steel cords 8a are disposed so as to intersect each other on the opposite sides between adjacent layers. The upper limit of the number of plies is not particularly limited, but is preferably 2 plies or 4 plies, particularly 2 plies.

  Setting the cord angle α of the bias belt layer 8 in the range of 45 to 65 degrees means that the cord angle α of the steel cord 8a is at or near the equilibrium angle. According to the theory of mechanics for cord reinforced composites, when a tensile load is applied to a cord reinforced rubber / plastic composite, the reinforcement cord is at an angle of 54.7 degrees with respect to the direction of the tensile load. The composite material maintains an undeformed state that does not stretch or shrink with respect to the tensile load. The cord angle (54.7 degrees) when this non-deformed state is reached is called the equilibrium angle.

  Therefore, the bias belt layer 8 hardly deforms with respect to the tension in the tire circumferential direction, so that no shear deformation occurs between the adjacent 0 degree belt layers 7 and between the bias belt layers 8. Therefore, coupled with the effect of improving the rigidity of the 0-degree belt layer 7 in the tire circumferential direction, the ground contact shape is a square as shown by a broken line B in FIG. 3 and greatly contributes to the improvement of tire durability and uneven wear resistance. Can do.

  The protective belt layer 9 disposed outside the bias belt layer 8 is a belt layer in which the cord angle β of the steel cord 9a with respect to the tire circumferential direction is 15 to 30 degrees. Since the bias belt layer 8 contributes to the improvement of the in-plane bending rigidity of the steel cord belt layer 6, it contributes to further improving the uneven wear prevention effect of the tire. When the cord angle β is less than 15 degrees, the interlaminar shear stress increases, so that peeling of the edge portion occurs. When the cord angle β exceeds 30 degrees, the effect of improving the in-plane rigidity decreases.

In the steel cord belt layer 6 according to the present invention, the width Wo of the 0 degree belt layer 7 is preferably in the range of 75 to 85% of the total tire width W as described above. The width Wb of the bias belt layer 8 is preferably smaller than the width Wo of the 0-degree belt layer 7 and in the range of 60 to 80% of the total tire width W. Furthermore, the width Wp of the protective belt layer 9 is preferably smaller than the width Wb of the bias belt layer 8 and in the range of 25 to 70% of the total tire width W. By setting to such a range, the durability and uneven wear resistance of the tire can be further improved. The present invention is applied to a heavy-duty flat pneumatic radial tire, and the flatness is particularly 60. %, It is possible to exert particularly excellent effects.

  When manufacturing a flat heavy load pneumatic radial tire having a tire cord size of 435 / 45R22.5 and having a steel cord belt layer, five types of belt layers constituting the steel cord belt layer are differentiated as follows. A pneumatic radial tire was manufactured (in the belt layer, the carcass layer side is the first layer, and the second layer, the third layer,... Are sequentially arranged toward the tread side).

Example 1
First layer (0 degree belt layer);
Belt width; 75% of total tire width W
Cord angle; 0 degree
Cord structure: 3 x (1 + 5) x 0.25mm, 25 ends / 50mm
Second layer (0 degree belt layer);
Belt width; 75% of total tire width W
Cord angle; 0 degree
Cord structure: 3 x (1 + 5) x 0.25mm, 25 ends / 50mm
Third layer (bias belt layer);
Belt width; 53% of total tire width W
Cord angle: 50 degrees (left tilt)
Cord structure: 3 + 9 × 0.22mm, 21 ends / 50mm
4th layer (bias belt layer);
Belt width; 48% of total tire width W
Cord angle: 50 degrees (right tilt)
Cord structure: 3 + 9 × 0.22mm, 21 ends / 50mm

(Example 2)
First layer (0 degree belt layer);
Belt width; 75% of total tire width W
Cord angle; 0 degree
Cord structure: 3 x (1 + 5) x 0.25mm, 25 ends / 50mm
Second layer (0 degree belt layer);
Belt width; 75% of total tire width W
Cord angle; 0 degree
Cord structure: 3 x (1 + 5) x 0.25mm, 25 ends / 50mm
Third layer (bias belt layer);
Belt width; 53% of total tire width W
Cord angle: 50 degrees (left tilt)
Cord structure: 3 + 9 × 0.22mm, 21 ends / 50mm
4th layer (bias belt layer);
Belt width; 48% of total tire width W
Cord angle: 50 degrees (right tilt)
Cord structure: 3 + 9 × 0.22mm, 21 ends / 50mm
5th layer (bias belt layer);
Belt width; 29% of total tire width W
Cord angle: 20 degrees (right tilt)
Cord structure: 3 x 0.20 mm + 6 x 0.35 mm, 15 ends / 50 mm

(Example 3)
First layer (0 degree belt layer);
Belt width; 75% of total tire width W
Cord angle; 0 degree
Cord structure: 3 x (1 + 5) x 0.25mm, 25 ends / 50mm
Second layer (0 degree belt layer);
Belt width: Two belt layers of 25% of the total tire width W are arranged with an interval of 27% of the total tire width W.
Cord angle; 0 degree
Cord structure: 3 x (1 + 5) x 0.25mm, 25 ends / 50mm
Third layer (bias belt layer);
Belt width; 53% of total tire width W
Cord angle: 50 degrees (left tilt)
Cord structure: 3 + 9 × 0.22mm, 21 ends / 50mm
4th layer (bias belt layer);
Belt width; 48% of total tire width W
Cord angle: 50 degrees (right tilt)
Cord structure: 3 + 9 × 0.22mm, 21 ends / 50mm

(Comparative Example 1)
First layer (bias belt layer):
Belt width; 68% of total tire width W
Cord angle: 50 degrees (left tilt)
Cord structure: 3 + 9 × 0.32mm, 21 ends / 50mm
Second layer (bias belt layer):
Belt width; 75% of total tire width W
Cord angle: 20 degrees (right tilt)
Cord structure: 3 + 9 × 0.32mm, 21 ends / 50mm
Third layer (bias belt layer):
Belt width; 71% of total tire width W
Cord angle: 20 degrees (left tilt)
Cord structure: 3 + 9 × 0.32mm, 21 ends / 50mm
Fourth layer (bias belt layer):
Belt width; 52% of total tire width W
Cord angle: 20 degrees (right tilt)
Cord structure: 3 x 0.20 mm + 6 x 0.35 mm, 15 ends / 50 mm

(Comparative Example 2)
First layer (bias belt layer):
Belt width; 75% of total tire width W
Cord angle: 20 degrees (left tilt)
Cord structure: 3 + 9 × 0.32mm, 21 ends / 50mm
Second layer (0 degree belt layer):
Belt width; 64% of total tire width W
Cord angle; 0 degree
Cord structure: 3 × (1 + 5) × 0.24mm, 21 ends / 50mm
Third layer (bias belt layer):
Belt width; 71% of total tire width W
Cord angle: 20 degrees (right tilt)
Cord structure: 3 + 9 × 0.32mm, 21 ends / 50mm
Fourth layer (bias belt layer):
Belt width; 52% of total tire width W
Cord angle: 20 degrees (left tilt)
Cord structure: 3 + 9 × 0.32mm, 21 ends / 50mm

  When “indoor durability” and “uneven wear resistance” were measured for the above five types of tires under the following test conditions, the results shown in Table 1 were obtained. The tires of Examples 1 to 3 all had improved durability and uneven wear resistance as compared with the tires of Comparative Examples 1 and 2.

[Indoor durability]
After filling the test tire with air pressure of 900 kPa and using a drum testing machine with a drum diameter of 1707 mm, after finishing the durability test specified in JIS D 4230, the tire breaks while increasing the load by 10% every 10 hours The distance traveled was measured.

  The evaluation is shown by an index with the running distance of the tire of Comparative Example 1 as 100. The larger the index value, the better the indoor durability.

[Uneven wear resistance]
When the test tire was mounted on a real vehicle and traveled 5000 km, the difference in wear amount between the tread center portion and both end portions was measured.

  The evaluation was performed by using the reciprocal of the measured value, and indicated by an index with the reciprocal of the tire of Comparative Example 1 being 100. The larger the index value, the better the uneven wear resistance.

1 is a meridian cross-sectional view showing a heavy load flat pneumatic radial tire according to an embodiment of the present invention. FIG. 2 is a partial development view of a steel cord belt layer of the tire of FIG. 1 viewed from the outside in the radial direction. It is a top view which shows the contact shape of the flat pneumatic tire for heavy loads.

Explanation of symbols

1 tread 4 carcass layer 6 steel belt layer 7 0 degree belt layer 7
8 Bias belt layer 9 Protective belt layer 9
4a, 7a, 8a, 9a Steel cord

Claims (6)

  In a heavy-duty flat pneumatic radial tire in which a plurality of ply steel cord belt layers are arranged on the outer periphery of the carth layer, the steel cord belt layer is arranged immediately above the carcass layer, and the cord angle with respect to the tire circumferential direction is substantially 0 degree belt layer of at least 1 ply which is 0 degree, and at least 2 plies which are arranged on the outer peripheral side of the 0 degree belt layer and have a substantially balanced angle in the range of 45 to 65 degrees cord angle with respect to the tire circumferential direction Heavy duty flat pneumatic radial tire composed of a bias belt layer.   The heavy-duty flat pneumatic radial tire according to claim 1, wherein a protective belt layer made of a steel cord having a cord angle of 15 to 30 degrees with respect to a tire circumferential direction is further arranged on the outer peripheral side of the bias belt layer.   The width of the 0 degree belt layer is 75 to 85% of the total tire width, the width of the bias belt layer is narrower than the 0 degree belt layer, and is 60 to 80% of the total tire width. 2. A flat pneumatic radial tire for heavy loads as described in 2.   The flat pneumatic tire for heavy loads according to claim 3, wherein the width of the protective belt layer is narrower than that of the bias belt layer and is 25 to 70% of the total tire width.   The flat pneumatic radial tire for heavy loads according to any one of claims 1 to 4, wherein the 0 degree belt layer and the bias belt layer are arranged in two plies, and the protective belt layer is arranged in one ply. The flat pneumatic radial tire for heavy loads according to any one of claims 1 to 5, wherein the flatness of the tire is 60% or less.

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