JP2010064689A - Pneumatic radial tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for heavy load reducing separation failure in a belt layer by suppressing reduction of tensile rigidity of a steel cord as much as possible by suppressing fretting abrasion generated between a steel cord body and a wrapping filament in the steel cord constituting the belt layer. <P>SOLUTION: The steel cord 4S constituting the belt layer 4 is constituted by the steel cord body comprising a plurality of steel filaments 4a, 4b, 4c and the wrapping filament 4z helically wound on the periphery. The lapping filament 4z is constituted by a brass element wire. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heavy-duty pneumatic radial tire, and more particularly to a heavy-duty pneumatic radial tire that suppresses wear of a steel cord constituting a belt layer and improves tire durability.

  Generally, steel cords are used for the belt layer of pneumatic radial tires used in heavy-duty vehicles such as trucks and buses. These steel cords are subjected to compressive stress to form the steel cord body. In order to prevent fatigue of the filament to be broken, the steel cord body has been wound around with a wrapping filament in a spiral manner to enhance the binding property of the steel cord (for example, patent literature) 1).

However, in this type of steel cord, at the point contact portion between the filament constituting the steel cord main body and the wrapping filament, the steel cord tends to be worn by fretting wear due to repeated compressive stress. There is a problem in that the rigidity of the tire is reduced and the deformation of the tire is increased to cause a separation failure in the belt layer.
JP 2004-68213 A

  The object of the present invention is to eliminate the above-mentioned conventional problems, and to suppress the fretting wear that occurs between the steel cord main body and the wrapping filament in the steel cord constituting the belt layer. An object of the present invention is to provide a heavy-duty pneumatic radial tire that reduces separation failure in a belt layer by suppressing a decrease in rigidity as much as possible.

  The heavy-duty pneumatic radial tire of the present invention that achieves the above object includes a carcass layer made of a steel cord between a pair of left and right bead portions, and a belt made of a steel cord on the outer peripheral side of the carcass layer in the tread portion. In the heavy-duty pneumatic radial tire with the layers arranged, the steel cord of the belt layer is composed of a steel cord body composed of a plurality of steel filaments and a wrapping filament wound in a spiral around the steel cord body. The filament is made of a brass wire.

  Moreover, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(5).

(1) The winding interval of the wrapping filament is set to 4 mm or less. In this case, the winding interval of the wrapping filament is preferably 2 mm or more.
(2) The strand diameter of the wrapping filament is set to 0.10 to 0.25 mm.
(3) The brass wire is composed of an alloy of 60 to 70% by weight of copper and 30 to 40% by weight of zinc. In this case, brass plating may be applied to the surface of the steel filament in the steel cord body.
(4) The winding direction of the wrapping filament is opposite to the twisting direction of the outermost layer of the steel cord body.
(5) The twisted structure of the steel cord body was selected from 3 + 9 + 15, 3/9, 3 + 9, 3 + 8 + 13, 3/8 + 13, 4 + 9 + 14, 3 + 8, 1 + 18, 1 × 27, 3 + 7, 1 × 9, 7 × (3 + 9 + 15) Either.

  According to the present invention, the steel cord of the belt layer is composed of a steel cord main body composed of a plurality of steel filaments and a wrapping filament spirally wound around the steel cord body, and the wrapping filament is compared with the steel filament. Because it is made of soft and soft brass wire, the wrapping filament will be worn out early even if friction due to repeated compressive stress occurs between the steel filament of the steel cord body and the wrapping filament. Since the filament is prevented from being worn, the tensile rigidity of the steel cord is ensured, so that deformation of the tire can be suppressed, separation failure in the belt layer can be reduced, and tire durability can be improved.

  In addition, as the wear of the brass wire progresses, the steel cord body and the wrapping filament are in surface contact with each other, so that the progress of the wear of the brass wire is gradually suppressed and the steel cord is bundled for a long time. Thus, separation failure in the belt layer can be reduced.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a semi-sectional view showing an example of a heavy-duty pneumatic radial tire according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an example of a steel cord constituting a belt layer in the tire of FIG.

In FIG. 1, a heavy-duty pneumatic radial tire 1 according to the present invention has a carcass layer 3 made of a steel cord mounted between a pair of left and right bead portions 2 and 2, and on the outer peripheral side of the carcass layer 3 in a tread portion 5. Belt layers 4 made of steel cords (in the figure, 4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ ) are arranged.

  In the heavy-duty pneumatic radial tire 1 according to the present invention, the steel cord constituting the belt layer 4 is wrapped with a steel cord main body composed of a plurality of steel filaments and spirally wound around the steel cord as described below. And a wrapping filament made of brass wire.

  FIG. 2 is a cross-sectional view showing an example of a steel cord constituting the belt layer 4. In the present embodiment, the steel cord 4S has a core 4A composed of three steel filaments 4a and nine steels arranged on the outer peripheral side. A steel cord body made up of a first sheath 4B made of a filament 4b and a second sheath 4C made of 15 steel filaments 4c arranged on the outer periphery thereof, and one brass element wound around the periphery of the steel cord body And a wrapping filament 4z made of a wire.

  Thus, by wrapping the wrapping filament 4z made of a brass wire softer than the steel filament 4c around the steel cord body, friction due to repeated compression occurs between the steel filament 4c and the wrapping filament 4z. However, since the wrapping filament 4z is worn early and suppresses the wear of the steel filament 4c in the steel cord body, the tensile rigidity of the steel cord 4S can be secured and the deformation of the tire can be suppressed. Separation failure in the belt layer 4 is reduced, and tire durability can be improved.

  In addition, since the steel cord body and the wrapping filament 4z are in surface contact with the progress of wear of the brass wire, the progress of the wear of the brass wire is gradually suppressed, and the steel cord 4S is used for a long time. Thus, the separation failure in the belt layer 4 can be reduced.

In the embodiment of FIG. 1, the belt layer 4 arranged on the outer peripheral side of the carcass layer 3 in the tread portion 5 is exemplified by four belt layers 4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ . The number of belt layers 4 is not limited to this. When the belt layer 4 is composed of a plurality of sheets, the steel cord 4S described above need not be applied to all the belt layers 4, and a conventional belt in which the wrapping filament 4z is composed of steel strands. Can be placed in combination with a layer.

  In the embodiment of FIG. 2, the steel cord main body in the steel cord 4S has a twist structure of 3 + 9 + 15, and the wrapping filament 4z is composed of one piece. However, the heavy load pneumatic radial of the present invention is illustrated. The structure of the steel cord 4S used for the belt layer 4 of the tire 1 is not limited to this. The steel cord body is composed of a plurality of steel filaments, and the wrapping filament 4z is composed of two or more brass strands. The case where it consists of a filament is included.

  In the present invention, the winding interval of the wrapping filament 4z is appropriately set according to the structure of the steel cord 4S and the wire diameter, but is preferably set to 4 mm or less. The lower limit is preferably set to 2 mm or more. Here, when the winding interval exceeds 4 mm, the bundling property of the steel cord 4S is lowered, and at the same time, the compression fatigue resistance of the belt layer 4 is lowered. When the winding interval is less than 2 mm, the productivity of the steel cord 4S is remarkably lowered. It will be.

  The winding interval mentioned above refers to the winding pitch of the wrapping filament 4z when the wrapping filament 4z is composed of one piece, and when the wrapping filament 4z is composed of a plurality of pieces, the respective wrapping intervals are used. This is the interval between the steel filament 4z and the longitudinal direction of the steel cord 4S. Accordingly, when a plurality of wrapping filaments 4z are formed, each wrapping filament 4z may be wound at intervals of 4 mm or less and 2 mm or more in the longitudinal direction of the steel cord body.

  More preferably, the strand diameter of the wrapping filament 4z described above is set to 0.10 to 0.25 mm, preferably 0.15 to 0.20 mm. If the wire diameter is less than 0.10 mm, it becomes difficult to prevent breakage during twisting, and if it exceeds 0.25 mm, the durability of the brass wire is lowered and the thickness of the rubber covering the steel cord 4S is reduced. This will increase the tire weight.

  In the present invention, the brass wire constituting the wrapping filament 4z is preferably composed of an alloy of 60 to 70% by weight of copper and 30 to 40% by weight of zinc. Thereby, the ductility of the wrapping filament 4z can be ensured while ensuring good adhesion to the surrounding rubber, and disconnection of the wrapping filament 4z can be prevented during the stranded wire processing.

  More preferably, among the steel filaments constituting the steel cord body, at least the surface of the steel filament 4c constituting the outermost layer is preliminarily plated with brass. As a result, the adhesion between the steel cord body and the wrapping filament 4z can be improved, the compression fatigue resistance of the steel cord 4S can be reliably ensured, and the adhesion to rubber can also be improved.

  The winding direction of the wrapping filament 4z in the steel cord 4S described above is preferably opposite to the twisting direction of the outermost layer (steel filament 4c in FIG. 2) of the steel cord body. Thereby, the bundling property of the steel cord 4S is enhanced, and the compression fatigue resistance can be secured at a high level.

  As described above, in the embodiment of FIG. 2, the case where the twisted structure of the steel cord body in the steel cord 4S is 3 + 9 + 15 is exemplified. However, in the belt layer 4 in the heavy-duty pneumatic radial tire 1 of the present invention, the steel cord In addition to the 3 + 9 + 15 mentioned above, the twisted structure of the main body may be 3/9, 3 + 9, 3 + 8 + 13, 3/8 + 13, 4 + 9 + 14, 3 + 8, 1 + 18, 1 × 27, 3 + 7, 1 × 9, 7 × (3 + 9 + 15), etc. is there.

  As described above, the heavy-duty pneumatic radial tire of the present invention is composed of a steel cord body made of a plurality of steel filaments and a wrapping filament spirally wound around the steel cord used for the belt layer. By configuring this wrapping filament with brass wire, the fretting wear that occurs between the steel filament of the steel cord body and the wrapping filament is suppressed, and the belt cord tension stiffness is prevented from being lowered and the tire durability is reduced. In particular, it is preferably applied to a heavy-duty pneumatic radial tire having a large load.

The tire size is 295 / 80R22.5, the tire structure is as shown in FIG. 1, the specifications of the four belt layers are shown in Table 1, and the material of the wrapping filament in the intermediate belt layers 4 ₂ and 4 ₃ is steel. A tire (conventional example) and a wrapping filament made of brass (alloy of 63% by weight of copper and 37% by weight of zinc), and different in wire diameter and winding pitch as shown in Table 2 Inventive tires (Examples 1 to 3) were each prepared in five.

  In Table 2, the twist pitch of each filament in the steel cord body is displayed as “winding pitch”, and the arrangement angle of the steel cord on the tire equator line with respect to the tire circumferential direction is displayed as “cord inclination angle”.

  The tire durability of these four types of tires was evaluated by the following test method, and the results are also shown in Table 2 using an index with the conventional example being 100. It shows that it is excellent in durability, so that a numerical value is large.

[Evaluation of tire durability]
Each tire is assembled into a rim (rim size: 22.5 × 8.25) and filled with an air pressure of 850 kPa. Then, the load is 51.5 kN and the speed is 45 km / h using an indoor drum tester (drum diameter: 1707 mm). It traveled 25,000 km. Each tire after running was cut into tread pieces having a circumferential length of 20 cm at six locations on the circumference, and these six tread pieces were disassembled to measure the average length of separation generated in the belt layer. This operation was performed for each of five tires, and the tire durability was evaluated using the reciprocal of the average value.

  From Table 2, it can be seen that the tire of the present invention is superior in tire durability as compared with the conventional tire.

1 is a half sectional view showing an example of a heavy-duty pneumatic radial tire according to an embodiment of the present invention. It is sectional drawing which shows an example of the steel cord which comprises the belt layer in the tire of FIG.

Explanation of symbols

1 Pneumatic tire for heavy load 2 Bead part 3 Carcass layer 4 Belt layer 4S Steel cord 4a, 4b, 4c Steel filament 4z Wrapping filament 5 Tread part

Claims (8)

In a heavy-duty pneumatic radial tire in which a carcass layer made of a steel cord is mounted between a pair of left and right bead portions, and a belt layer made of a steel cord is arranged on the outer peripheral side of the carcass layer in a tread portion,
The steel cord of the belt layer is composed of a steel cord main body composed of a plurality of steel filaments and a wrapping filament wound spirally around the steel cord body, and the wrapping filament is composed of brass wire for heavy load pneumatic Radial tire.   The heavy-duty pneumatic radial tire according to claim 1, wherein a winding interval of the wrapping filament is 4 mm or less.   The heavy-duty pneumatic radial tire according to claim 2, wherein a winding interval of the wrapping filament is 2 mm or more.   The pneumatic radial tire for heavy loads according to any one of claims 1 to 3, wherein a strand diameter of the wrapping filament is 0.10 to 0.25 mm.   The heavy-duty pneumatic radial tire according to any one of claims 1 to 4, wherein the brass wire is made of an alloy of 60 to 70% by weight of copper and 30 to 40% by weight of zinc.   The pneumatic radial tire for heavy loads according to any one of claims 1 to 5, wherein the surface of the steel filament in the steel cord body is plated with brass.   The heavy-duty pneumatic radial tire according to any one of claims 1 to 6, wherein a winding direction of the wrapping filament is opposite to a twisting direction of the outermost layer of the steel cord main body.   The steel cord body has a twisted structure selected from 3 + 9 + 15, 3/9, 3 + 9, 3 + 8 + 13, 3/8 + 13, 4 + 9 + 14, 3 + 8, 1 + 18, 1 × 27, 3 + 7, 1 × 9, 7 × (3 + 9 + 15) The pneumatic radial tire for heavy loads according to any one of claims 1 to 7.

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