JP2008044536A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of enhancing the durability by preventing peeling of rubber around an organic fiber cord constituting a belt cover layer on an edge part of a belt layer. <P>SOLUTION: In the pneumatic radial tire T, a belt layer 6 is arranged on an outer circumferential side of a carcass layer 5 of a tread part 1, and a belt cover layer 8 with an organic fiber cord 7 being wound around in the circumferential direction of the tire on at least an outer circumferential side of an edge part of the belt layer 6 is provided. A rubber fiber compound layer 9 containing short fibers is interposed between the belt cover layer 8 and the edge part of the belt layer 6, and the short fibers are oriented at the angle of 60-120° with respect to the circumferential direction of the tire in the rubber fiber compound layer 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire that prevents rubber peeling at a belt layer edge portion in a tire provided with a belt cover layer and improves load durability.

  Generally, in a pneumatic radial tire designed for high-speed running, an organic fiber cord is continuously wound in a spiral shape in the tire circumferential direction so as to cover at least the edge portion on the outer peripheral side of the belt layer provided in the tread portion. The belt cover layer is arranged to prevent the belt layer from being lifted by centrifugal force when traveling at a high speed and to prevent peeling. Further, the belt cover layer increases the rigidity of the shoulder portion of the tread, and thus has an effect of improving road noise.

  However, it has been found that when the load applied to the tire during traveling is high, there is a new problem that rubber breakage tends to occur as described below.

  As shown in FIG. 3A, when the tire T comes into contact with the road surface, the tread portion is compressively deformed by the load of the vehicle, and this compressive deformation is repeated by rotation in the rotation direction R. As shown in FIG. 3B, the force acting on the shoulder portion of the tread portion on the ground surface 11 is the rubber adjacent to the belt cover layer at the same time as the tensile force Fs in the tire circumferential direction acts on the organic fiber cord 12. , A tensile force Fr in the tire width direction and a compressive force fr ′ in the tire circumferential direction act as the reaction force. Therefore, the shear strain is generated by the tensile force Fs of the organic fiber cord 12 in the tire circumferential direction and the compressive force fr ′ of the rubber, and the shear strain causes rubber peeling at the edge portion of the belt layer.

As a countermeasure, for example, it is considered effective to interpose a rubber fiber layer containing short fibers between the belt layer edge portion and the belt cover layer as disclosed in Patent Document 1. However, sufficient load durability cannot be obtained simply by disposing a rubber fiber layer containing short fibers.
Japanese Patent Laid-Open No. 10-44711

  An object of the present invention is to provide a pneumatic radial tire that prevents rubber peeling at a belt layer edge portion in a tire provided with a belt cover layer and improves load durability.

  The pneumatic radial tire of the present invention that achieves the above object is a belt in which a belt layer is disposed on the outer circumferential side of a carcass layer of a tread portion, and an organic fiber cord is wound in the tire circumferential direction on at least the outer circumferential side of the belt layer. In a pneumatic radial tire provided with a cover layer, a rubber fiber composite layer including short fibers is interposed between the belt cover layer and the belt layer edge portion, and the short fibers are in the tire circumferential direction in the rubber fiber composite layer. It is characterized by being oriented at an angle of 60 ° to 120 ° with respect to the angle.

  In the pneumatic radial tire of the present invention, a rubber fiber composite layer including short fibers is interposed between the organic fiber cord of the belt cover layer and the belt layer edge portion, and the short fibers are arranged in the tire circumferential direction in the rubber fiber composite layer. On the other hand, since it is oriented mainly in the tire width direction in the range of 60 ° to 120 °, in order to increase the tensile rigidity in the tire width direction of the rubber fiber composite layer and to suppress the shear strain of the belt cover layer with respect to the organic fiber cord. Rubber peeling can be prevented and load durability can be improved.

  FIG. 1 is a meridional direction sectional view showing an example of a pneumatic radial tire of the present invention.

  In FIG. 1, a pneumatic radial tire T includes a tread portion 1, a sidewall portion 2, and a bead portion 3, and a carcass layer 5 is mounted between a pair of left and right bead cores 4 embedded in the bead portion 3. Each part is folded around the bead core 4 from the inside of the tire to the outside. A belt layer 6 of a plurality of plies (2 plies in the illustrated example) is disposed over the circumference of the tire on the outer circumferential side of the carcass layer 5 of the tread portion 1, and the organic fiber cord 7 is disposed on the outer circumferential side of the edge of the belt layer 6. The belt cover layer 8 is formed by continuously winding in a spiral direction. The belt cover layer 8 is not limited to an edge cover that covers only the edge portion of the belt layer 6 as shown in the figure, and may be a full cover that covers the entire width of the belt layer 6, or a full cover and an edge cover. And both of them may be provided.

  Further, a rubber fiber composite layer 9 including short fibers 10 is interposed between the belt cover layer 8 and the edge portion of the belt layer 6. In this rubber fiber composite layer 9, the short fibers 10 are oriented at an angle θ of 60 ° to 120 ° with respect to the tire circumferential direction C as shown in FIG. In the illustrated example, the rubber fiber composite layer 9 is interposed between the edge portion of the belt layer 6 as an auxiliary rubber layer independent of the belt cover layer 8. Instead of inserting a layer, the coating rubber of the belt cover layer 8 may be a rubber fiber composite layer.

  In the present invention, examples of the organic fiber cord 12 of the belt cover layer 8 include aliphatic polyamide fibers, polyester fibers, polyketone fibers, and aromatic polyamide / aliphatic polyamide composite fibers.

  In the present invention, the short fibers 10 blended in the rubber fiber composite layer 9 must be oriented in the range of an angle θ of 60 ° to 120 ° with respect to the tire circumferential direction C. By aligning the short fibers in this way, the rubber fiber composite layer has high tensile rigidity, particularly in the tire width direction. Accordingly, since the deformation of the rubber fiber composite layer is reduced with respect to the tensile force in the width direction acting on the rubber layer of the shoulder portion at the time of ground contact, the compressive deformation in the tire circumferential direction due to the reaction force is also reduced. For this reason, the shear strain due to the difference between the tensile force in the circumferential direction of the organic fiber cord and the compressive force in the circumferential direction of the rubber fiber composite layer is also reduced, so that the rubber layer is prevented from peeling at the edge of the belt layer and the load durability is improved. Can be improved.

  If the angle θ formed by the short fiber in the tire circumferential direction C is out of the above range, the tensile rigidity in the tire width direction cannot be sufficiently increased, and shear strain on the organic fiber cord cannot be reduced. The improvement of property cannot be obtained. The orientation angle θ of the short fibers is more preferably 80 ° to 100 °.

  The short fiber used in the present invention is not particularly limited, but is at least one selected from aliphatic polyamide fiber, aromatic polyamide fiber, polyester fiber, polyketone fiber, polyvinyl alcohol fiber, glass fiber, and carbon fiber. Preferably there is. By using such short fibers, the rubber layer can be effectively reinforced.

  The diameter of the short fiber is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 1.0 μm. If the diameter of the short fiber is less than 0.1 μm, the cost becomes high and practical application is difficult, and if it exceeds 10 μm, the durability may be insufficient.

  Moreover, the length of the short fiber is preferably 40 μm to 400 μm, more preferably 40 μm to 200 μm. If the length of the short fiber is less than 40 μm, it becomes difficult to align the direction of orientation of the short fiber, and if it exceeds 400 μm, the fibers may be entangled with each other and may cause a failure.

  The short fiber content in the rubber fiber composite layer is preferably 3 to 30% by weight, more preferably 3 to 10% by weight. If the short fiber content is less than 3% by weight, uniformity of orientation cannot be maintained, and if it exceeds 30% by weight, interface failure of short fibers is likely to occur inside the rubber fiber composite layer, resulting in durability. May decrease.

  In the present invention, the short fiber is preferably surface-treated with an aqueous condensate (RFL) of resorcin (R) / formaldehyde (F) initial condensate (RF) and rubber latex (L). By such surface treatment, the affinity between the short fibers and the rubber can be increased, and the tensile rigidity in the orientation direction of the short fibers can be further increased.

  The initial condensate (RF) was prepared by dissolving resorcin (R) and an aqueous formalin solution in water, and adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide as a catalyst to react R and F. There is a resol type or a novolac type in which R and F are reacted under an acidic catalyst such as oxalic acid and hydrochloric acid, and any of them may be used.

  The rubber latex (L) to be mixed with the initial condensate (RF) is appropriately selected according to the type of rubber constituting the rubber fiber composite layer. For example, vinylpyridine / styrene / butadiene terpolymer latex, SBR latex, natural rubber Latex and the like are preferred. The surface treatment can be carried out by impregnating or adhering an aqueous mixed liquid (RFL) to the fiber cord before being cut into short fibers and heat-treating the fiber cord.

  The rubber composing the rubber fiber composite layer may be any rubber usable for tires, such as natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR). And diene rubbers such as butyl rubber (IIR), and the like can be used alone or as any blend.

  In the present invention, when the coating rubber of the belt cover layer is composed of a rubber fiber composite layer, the formation method is as follows. Short fibers are mainly formed on the outer peripheral side of the belt layer edge portion when molding an unvulcanized tire. A rubber sheet oriented in the width direction is wound, an organic fiber cord is wound spirally thereon, and a rubber sheet in which short fibers are substantially oriented in the width direction or a rubber sheet not blended with short fibers is wound thereon, It can be formed by bonding.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  As shown in FIG. 1, the tire size is 195 / 65R15, the tire structure is a polyketone fiber cord for the belt cover layer, and the rubber fiber composite layer including the short fibers of nylon 66 fibers is used as a common condition. Five types of pneumatic radial tires (Examples 1 to 3 and Comparative Examples 1 and 2) with different orientation angles, diameters, lengths, and contents in the circumferential direction as shown in Table 1 were produced. As a conventional example, a pneumatic radial tire similar to that of Example 1 was manufactured except that the rubber fiber composite layer was not provided.

  With respect to the obtained six types of pneumatic radial tires (Examples 1 to 3, Comparative Examples 1 and 2, and conventional examples), load durability was measured by the test method described below, and the results are shown in Table 1. .

Load durability test The obtained pneumatic radial tire was continuously increased by 5% every 5 hours after the end of the durability test under the JIS D4230 and JATMA specified load on a drum testing machine with a drum diameter of 1707 mm. The load when the tire broke down was measured. The test results are represented by an index in which the load value of each tire is 100 as the load value of the conventional example. It shows that load durability is excellent, so that this index | exponent becomes large.

  As is apparent from Table 1, it was recognized that the pneumatic radial tires (Examples 1 to 3) of the present invention have significantly improved load durability compared to the conventional tires. On the other hand, those in which the orientation direction of the short fibers in the rubber fiber composite layer is in the circumferential direction (Comparative Examples 1 and 2) were insufficiently improved in load durability.

It is meridian direction sectional drawing which shows an example of the pneumatic radial tire of this invention. It is a model enlarged view which shows an example of the orientation direction of the short fiber of the rubber fiber composite layer in the pneumatic radial tire of this invention. It is explanatory drawing of the grounding surface of a pneumatic radial tire, and the force which acts there, (A) is a tire side view, (B) is a model enlarged view around the organic fiber cord of the belt cover layer in a tire grounding surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 5 Carcass layer 6 Belt layer 7 Organic fiber cord 8 Belt cover layer 9 Rubber fiber composite layer 10 Short fiber T Pneumatic radial tire

Claims (7)

In a pneumatic radial tire in which a belt layer is arranged on the outer circumferential side of the carcass layer of the tread, and a belt cover layer in which an organic fiber cord is wound in the tire circumferential direction is provided on at least the outer circumferential side of the belt layer.
A rubber fiber composite layer containing short fibers is interposed between the belt cover layer and the belt layer edge portion, and the short fibers are at an angle of 60 ° to 120 ° with respect to the tire circumferential direction in the rubber fiber composite layer. A pneumatic radial tire that is oriented.   The pneumatic radial tire according to claim 1, wherein the rubber fiber composite layer is a coating rubber constituting the belt cover layer.   The pneumatic radial tire according to claim 1, wherein the rubber fiber composite layer is an auxiliary rubber layer disposed between the belt cover layer and the belt layer edge portion.   The pneumatic according to claim 1, 2, or 3, wherein the short fibers are at least one selected from aliphatic polyamide fibers, aromatic polyamide fibers, polyester fibers, polyketone fibers, polyvinyl alcohol fibers, glass fibers, and carbon fibers. Radial tire.   The pneumatic radial tire according to any one of claims 1 to 4, wherein the short fibers have a diameter of 0.1 µm to 10 µm and a length of 40 µm to 400 µm.   The pneumatic radial tire according to any one of claims 1 to 5, wherein a content of the short fibers in the rubber fiber composite layer is 3 to 30% by weight. The said short fiber is surface-treated with the aqueous | water-based liquid mixture (RFL) of the initial condensate (RF) of resorcinol (R) and formaldehyde (F), and rubber latex (L). Pneumatic radial tires.

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