JP5109487B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire, and more specifically, in a pneumatic tire in which a wound end of a carcass layer is extended to the inside of a belt layer, even when used under conditions of high internal pressure and high load, The present invention relates to a pneumatic radial tire that prevents separation at a winding end of a carcass layer.

  Conventionally, tires that are used under conditions of high internal pressure and high load, such as light truck tires, have used organic fiber cords for the carcass layer and demanded around the bead due to demands for manufacturing simplicity and weight reduction. Some have a simple structure.

On the other hand, some passenger car tires have a carcass layer winding terminal extending below the belt layer for the purpose of handling stability (see, for example, Patent Document 1). However, when such a carcass layer configuration is applied to a tire that is used under conditions of high internal pressure and high load such as a small truck tire, separation occurs from the carcass layer winding terminal, and durability is reduced. There was a problem.
JP 2004-352174 A

  The object of the present invention is to eliminate the above-mentioned problems, and is used under conditions of high internal pressure and high load in a pneumatic tire in which a wound end of a carcass layer made of an organic fiber cord extends to the inside of a belt layer. Even in such a case, it is an object of the present invention to provide a pneumatic radial tire that prevents separation at the rolled-up end portion of the carcass layer and improves durability.

In order to achieve the above object, a pneumatic radial tire according to the present invention includes a carcass layer made of at least one organic fiber cord and a belt layer made of at least two steel cords, and has a rolled-up end portion of the carcass layer. In a pneumatic radial tire having both surfaces extending to the inside of the end portion of the belt layer, the wound end portion of the carcass layer is covered with a rubber sheet made of a rubber composition having a tan δ at 60 ° C. of 0.15 to 0.25. The covering width of the rubber sheet is 10 to 30 mm per side, and the carcass layer is 45 to 65 organic fiber cords having a diameter of 1000 to 2000 T / 2 made of polyester fiber, rayon fiber, or nylon fiber per 5 cm. It is characterized by being arranged in parallel and covered with rubber so as to have a density of .

Moreover, in the structure mentioned above, it is preferable to comprise as described in (1)-( 4 ) below .
(1 ) The thickness of the rubber sheet is 0.5 to 1.0 mm.
( 2 ) The overlapping width of the winding end of the carcass layer and the belt layer is set to 5 to 20 mm.
( 3 ) The angle of the organic fiber cord with respect to the tire circumferential direction is set to 70 to 88 °.
( 4 ) Applicable to small truck tires using JATMA maximum air pressure of 350 to 650 kPa.

  According to the present invention, in the configuration in which the wound end portion of the carcass layer made of at least one organic fiber cord extends to the inside of the end portion of the belt layer, the tan δ at 60 ° C. of the carcass layer is 0. By covering with a rubber sheet comprising a rubber composition of 15 to 0.25, even when used under conditions of high internal pressure and high load, due to the difference in rigidity between the rolled-up end of the carcass layer and the surrounding rubber Since the rubber sheet suppresses the generated heat, separation at the rolled-up end of the carcass layer can be prevented and durability can be improved.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a half sectional view showing the arrangement of a carcass layer and a belt layer in a pneumatic radial tire according to an embodiment of the present invention, and FIG. 2 is a partial sectional view showing an enlarged main part in FIG.

  In FIG. 1, a pneumatic radial tire 1 includes a pair of left and right bead portions 2, 2 mounted with a carcass layer 3 made of at least one layer (one layer in the figure) of an organic fiber cord, and an end portion of the carcass layer 3. 3a is wound around the bead cores 4 and 4 embedded in the bead portions 2 and 2 from the tire inner side toward the outer side, and the winding end portion 3a of the carcass layer 3 is extended to the inner side of the end portion of the belt layer 6. . The belt layer 6 is composed of two or more steel cords (two layers in the figure), and the belt layers 6 and 6 cross the directions of the cords between the layers.

  In the pneumatic radial tire 1 of the present invention, the tan δ at 60 ° C. is 0.15 to 0.25, preferably as shown in FIGS. It is covered with a rubber sheet 7 made of a rubber composition of 0.16 to 0.20.

  Thus, even when the pneumatic radial tire 1 is used under conditions of high internal pressure and high load, the rubber sheet 7 generates heat generated due to a difference in rigidity between the wound-up end portion 3a of the carcass layer 3 and the surrounding rubber. It can suppress and can prevent the separation in the winding-up edge part 3a of the carcass layer 3, and can improve durability.

The carcass layer 3 is constituted by covering rubber with a cord having a diameter of 1000 to 2000 T / 2 made of polyester fiber, rayon fiber, nylon fiber, etc., and arranged in parallel so as to have a density of 45 to 65 per 5 cm. The

  When the tan δ at 60 ° C. of the rubber sheet 7 is less than 0.15, the effect of preventing separation at the end portion 3a of the carcass layer 3 cannot be sufficiently obtained, and when it exceeds 0.25, the separation at the end portion 3a of the carcass layer 3 is conversely performed. It tends to occur.

  The tan δ of the rubber sheet 7 described above is a value when measured using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho) under the conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ± 2%, and a temperature of 60 ° C. Say.

The rubber sheet 7 mentioned above coat | covers both surfaces of the carcass layer 3 as shown to Fig.3 (a) according to the kind and magnitude | size of a tire. In this case, it is preferred that, when coated so as to cover both sides wrap terminals of the carcass layer 3 as shown in FIG. 3 (b). Further, as shown in FIG. 3C , a plurality of rubber sheets 7 may be laminated and covered.

In either case, the coating width w 10~30mm per one side of the carcass layer 3 of rubber sheet 7, preferably adjusted to be 13～26Mm. If the covering width w is less than 10 mm, the effect of preventing separation cannot be obtained sufficiently, and if it exceeds 30 mm, the tire weight increases.

  Furthermore, the thickness t of the rubber sheet 7 may be 0.5 to 1.0 mm, preferably 0.6 to 0.8 mm, per side of the carcass layer 3. If the thickness t is less than 0.5 mm, the effect of preventing separation cannot be sufficiently obtained. If the thickness t exceeds 1.0 mm, a step is formed in the vicinity of the end of the rubber sheet 7 at the time of molding the tire. It tends to occur.

  In the present invention, the overlap width CW (see FIG. 2) between the end 3a of the carcass layer 3 and the belt layer 6 may be adjusted to 5 to 20 mm, preferably 8 to 18 mm. That is, the distance between the terminal 3 b of the carcass layer 3 and the terminal 6 b of the belt layer 6 having the maximum width of the belt layers 6 and 6 may be adjusted to 5 to 20 mm. If the overlap width CW is less than 5 mm, separation is likely to occur in the vicinity of the end 6b of the belt layer 6, and if it exceeds 20 mm, the weight of the tire increases.

  The pneumatic radial tire 1 of the present invention is formed so that the arrangement angle of the organic fiber cord is typically 90 ° with respect to the tire circumferential direction. However, it has been found that the separation at the rolled-up end portion 3a of the carcass layer 3 is often seen in a tire in which the organic fiber cord is disposed at an angle of 88 ° or less with respect to the tire circumferential direction. From such a viewpoint, the angle of the organic fiber cord described above is 70 to 88 °, preferably 72 to 87 ° with respect to the tire circumferential direction. Thereby, the separation prevention effect in the winding edge part 3a of the carcass layer 3 of the present invention is most effectively exhibited. If the cord angle described above is less than 70 °, the basic functions of the tire such as riding comfort and durability are deteriorated, and the function as a radial tire cannot be performed.

  As described above, the pneumatic radial tire 1 of the present invention extends the winding end portion 3a of the carcass layer 3 made of an organic fiber cord to the inner side of the end portion of the belt layer 6 and the end portion 3a of the carcass layer 3 as well. By covering with a rubber sheet 7 made of a rubber composition having a tan δ at 60 ° C. of 0.15 to 0.25, separation at the end portion 3a of the carcass layer 3 is prevented, particularly under conditions of high internal pressure and high load. Therefore, it can be preferably applied to tires for light trucks that use JATMA-specified maximum air pressure of 350 to 650 kPa, preferably 450 to 600 kPa.

A conventional tire in which the tire size is 185R14LT 8PR, the basic structure of the tire is shown in FIG. 1, and the overlap width CW in FIG. 2 is different as shown in Table 1, and the end portion 3a of the carcass layer 3 is not covered with the rubber sheet 7 ( the conventional example), the coating width w and thickness h of the rubber sheet 7 while covering the rubber sheet 7, 0.20 tanδ at 60 ° C. depending on the form shown in FIG. 3 (b) to the end portion 3a of the carcass layer 3 The tires of the present invention (Examples 1 to 4) were made different from each other as shown in Table 1. The main specifications of the carcass layer in each tire were set as follows.
・ Organic fiber cord: Polyester fiber cord ・ Cord angle with respect to tire circumferential direction: 85 °
・ Number of cords: 31 / 5cm
For these five types of tires, load durability and high-speed durability were evaluated by the following test methods.

[Evaluation of load durability]
Each tire is assembled in a rim (14 × 5 1 / 2J) and filled with 450 kPa, using a drum tester with a drum diameter of 1707 mm, the speed is 81 km / h, and the load is 75% of the maximum load specified by JATMA The vehicle was run for 4 hours, 97% for 6 hours, and 114% for 24 hours, and then the load was increased by 19% every 8 hours, and the running distance until the tire broke was measured. The results are also shown in Table 1 in the index display where the conventional example is 100. The larger the value, the better.

[Evaluation of high-speed durability]
Each tire is assembled in a rim (14 × 5 1 / 2J) and filled with 450 kPa, using a drum tester with a drum diameter of 1707 mm, the speed is 81 km / h, and the load is 88% of the maximum load specified by JATMA The vehicle was run for 2 hours, and thereafter the running distance until the tire broke was measured while increasing the speed by 10 km / h every 30 minutes. The results are also shown in Table 1 in the index display where the conventional example is 100. The larger the value, the better.

  From Table 1, it can be seen that the tire of the present invention has improved load durability and high-speed durability compared to the conventional tire.

FIG. 2 is a half cross-sectional view showing an arrangement of a carcass layer and a belt layer in a pneumatic radial tire according to an embodiment of the present invention. It is a partial cross section figure which expands and shows the principal part in FIG. (A)- (c) is explanatory drawing which illustrates the coating | coated form of the rubber sheet by embodiment of this invention, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic radial tire 2 Bead part 3 Carcass layer 3a End part 3b Terminal 6 Belt layer 6b Terminal 7 Rubber sheet w Covering width t Thickness CW Overlap width

Claims (6)

A pneumatic radial tire comprising a carcass layer made of at least one layer of organic fiber cord and a belt layer made of at least two layers of steel cord, wherein the wound end of the carcass layer extends to the inside of the end of the belt layer. In
The both sides of the rolled-up end of the carcass layer are covered with a rubber sheet made of a rubber composition having a tan δ at 60 ° C. of 0.15 to 0.25 , and the covering width of the rubber sheet is 10 to 30 mm per side, The carcass layer was constituted by covering the rubber with an organic fiber cord made of polyester fiber, rayon fiber, or nylon fiber having a diameter of 1000 to 2000 T / 2 in parallel so as to have a density of 45 to 65 per 5 cm . Pneumatic radial tire. The pneumatic radial tire according to claim 1 , wherein the rubber sheet has a thickness of 0.5 to 1.0 mm per side . The pneumatic radial tire according to claim 1 or 2 , wherein an overlap width between the rolled-up end portion of the carcass layer and the belt layer is 5 to 20 mm. The pneumatic radial tire according to claim 1, 2 or 3 the angle is 70 to 88 ° with respect to the tire circumferential direction of the organic fiber cord. The pneumatic radial tire according to claim 1, 2, 3, or 4 , wherein the pneumatic tire is a light truck tire that uses a JATMA maximum air pressure of 350 to 650 kPa. The pneumatic radial tire according to claim 1, wherein the rubber sheet wraps an end of the carcass layer.

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