JP4428060B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire using a hybrid cord of an aliphatic polyketone, and more specifically, a pneumatic radial tire that achieves a reduction in rolling resistance and a reduction in road noise while ensuring durability. About.

  In a pneumatic radial tire, a belt reinforcing layer formed by winding a reinforcing cord in the tire circumferential direction is disposed on the outer peripheral side of the belt layer. It is known that by adding such a belt reinforcing layer, the rigidity in the tire circumferential direction in the tread portion is reinforced, and an improvement effect on road noise can be obtained. Nylon cords are generally used as the reinforcement cords for the belt reinforcement layer. However, in recent years, it has been proposed to use cords such as aliphatic polyketone, polyethylene terephthalate, and aromatic polyamide to enhance the reinforcement effect. (For example, refer to Patent Documents 1 to 3).

  However, the cord of the aliphatic polyketone has good adhesion to rubber, but its elongation is small. For example, when placed near the center of the tread, it follows the lift during vulcanization (expansion in the tire radial direction). Is difficult. On the other hand, polyethylene terephthalate cords have higher elasticity than nylon, but the reinforcing effect is not always sufficient, and they are inferior to nylon in terms of adhesion. In addition, the cord of the aromatic polyamide not only has poor adhesion, but also has a small elongation, so it is difficult to follow the lift during vulcanization.

For this reason, it has been difficult to simultaneously achieve a reduction in rolling resistance and a reduction in road noise while ensuring durability in comparison with nylon cords that are widely used.
JP 11-208212 A JP 2000-203212 A JP 2003-146010 A

  An object of the present invention is to provide a pneumatic radial tire that can simultaneously achieve a reduction in rolling resistance and a reduction in road noise while ensuring durability.

In order to achieve the above object, a pneumatic radial tire of the present invention is a belt in which a belt layer is disposed on the outer peripheral side of a carcass layer in a tread portion, and a reinforcing cord is wound around the outer peripheral side of the belt layer in the tire circumferential direction. in the pneumatic radial tire of arranging the reinforcing layer, wherein the reinforcing cords of the belt reinforcing layer, Rutotomoni using hybrid cord formed by twisting a fiber of the fiber and nylon polyketone, tire width direction the belt reinforcing layer The hybrid cord is disposed at the center portion of the belt reinforcing layer, and the aliphatic polyketone cord is disposed at both ends of the belt reinforcing layer. It is.

  In the present invention, a hybrid cord formed by twisting aliphatic polyketone fibers and nylon fibers is used as the reinforcing cord of the belt reinforcing layer. Since this hybrid cord exhibits adhesiveness equivalent to that of nylon, even when it is used for a belt reinforcing layer, good durability can be ensured. In addition, the hybrid cord has higher elasticity and greater reinforcement effect than nylon or polyethylene terephthalate, so that it can reduce rolling resistance and road noise. Furthermore, since the hybrid cord has a larger elongation than that of the aliphatic polyketone alone, it can follow the lift during vulcanization even when it is arranged in the center of the belt reinforcing layer.

In the present invention, the belt reinforcing layer is divided into a central portion and both end portions in the tire width direction, and a hybrid cord is disposed at the central portion of the belt reinforcing layer, while an aliphatic polyketone is formed at both end portions of the belt reinforcing layer. Place the code . In other words, by placing the hybrid cord in a portion where the lift is relatively large during vulcanization and placing the aliphatic polyketone cord in a portion where the lift is relatively small, the effect of reducing rolling resistance and road noise can be enhanced. .

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

  FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3 and 3, and an end portion of the carcass layer 4 is folded around the bead core 5 from the inside to the outside of the tire. On the outer peripheral side of the carcass layer 4 in the tread portion 1, a belt layer 6 is disposed over the entire tire circumference. These belt layers 6 include reinforcing cords that are inclined at an angle of 5 to 35 ° with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other. A steel cord is preferably used as the reinforcing cord of the belt layer 6, but the material is not particularly limited. Further, a belt reinforcing layer 7 formed by winding a reinforcing cord in the tire circumferential direction is arranged on the outer peripheral side of the belt layer 6.

In the pneumatic radial tire, a hybrid cord formed by twisting aliphatic polyketone fibers and nylon fibers is used as the reinforcing cord of the belt reinforcing layer 7. The aliphatic polyketone has a structure represented by the following formula (1).
_{- (CH 2 -CH 2 -CO)} n- (R-CO) m- ··· (1)

  Here, 1.05 ≧ (n + m) /n≧1.00, R is an alkylene group having 3 or more carbon atoms. By reducing the fraction of m, a cord having high strength, high dimensional stability, and high heat resistance can be obtained. In particular, it is preferable to use an alternating copolymer consisting essentially of ethylene and carbon monoxide, where m = 0. The alkylene group includes, for example, a propylene group.

  On the other hand, as nylon, polytetramethylene adipamide (nylon 46), polycoupleramide (nylon 6), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebamide (nylon 610), polyhexamethylene dodecamide (Nylon 612 etc. are mentioned, and nylon 66 is particularly preferable.

  The method of twisting these nylon fibers and aliphatic polyketone fibers is not particularly limited. The method of adding the upper twist after adding the respective lower twists to the respective fibers, For example, a method of adding a lower twist and further combining these combined twisted yarns and applying an upper twist may be used.

The hybrid cord preferably has a twist coefficient K represented by K = T × (D / 1.111) ^1/2 in the range of 800 to 2500. Here, T is the number of twists of the cord (times / 10 cm), and D is the total number of decitex of the cord. If the twist coefficient K is less than 800, the elongation of the cord becomes insufficient. Conversely, if it exceeds 2500, the modulus decreases greatly. Further, the total decitex number D of the code is preferably 1880 to 4200 dtex.

Next, the characteristics of the hybrid code will be described in comparison with other codes. Table 1 shows the physical properties of an aliphatic polyketone and nylon hybrid cord (POK / 66N), aliphatic polyketone cord (POK), polyethylene terephthalate cord (PET), and nylon cord (66N). In Table 1, the intermediate elongation is the elongation (%) when a load of 67 N is applied to the cord. The peeling force is a force required to vulcanize and bond two sheets of 25 mm width each having a cord embedded in rubber at a cord driving density of 50/50 mm and to peel them off at room temperature.

  As shown in Table 1, the hybrid cord has greater strength than nylon cord or polyethylene terephthalate cord, has a higher intermediate elongation than aliphatic polyketone cord, and has better adhesion than polyethylene terephthalate cord. Yes. Therefore, when the hybrid cord is used for a belt reinforcing layer of a pneumatic radial tire, it is possible to simultaneously achieve reduction in rolling resistance and reduction in road noise while ensuring durability.

  FIGS. 2A to 2B show a specific structure of the belt reinforcing layer in the present invention. As shown in FIGS. 2A to 2B, the belt reinforcing layer 7 disposed on the outer peripheral side of the belt layer 6 is divided into a center portion 7A and both end portions 7B and 7C in the tire width direction. The above-described hybrid cord is disposed at the central portion 7A of the belt reinforcing layer 7, and aliphatic polyketone cords are disposed at both end portions 7B and 7C of the belt reinforcing layer 7, respectively.

  In the above structure, since the hybrid cord is disposed in the central portion 7A of the belt reinforcing layer 7, the hybrid cord follows the lift during vulcanization in the central portion 7A and exhibits an excellent reinforcing effect. Become. On the other hand, aliphatic polyketone cords are arranged at both end portions 7B and 7C having a relatively small lift during vulcanization. Therefore, the reinforcing effect based on the highly elastic aliphatic polyketone cord can be obtained at both ends 7B and 7C.

FIGS. 3A to 3B show another structure (reference example) of the belt reinforcing layer. 3 (a) to 3 (b), the belt reinforcing layer 7 disposed on the outer peripheral side of the belt layer 6 is composed of the same reinforcing cord over the entire width, and the above-described hybrid cord is used as the reinforcing cord. Also in this case, the hybrid cord follows the lift during vulcanization and exhibits an excellent reinforcing effect.

In a pneumatic radial tire having a tire size of 195 / 60R15, five types of test tires (Example 1 , Reference Example 1 and Comparative Examples 1 to 1) in which the reinforcing cords of the belt reinforcing layer disposed on the outer peripheral side of the belt layer are varied. 3) was produced.

  These test tires were evaluated for road noise, rolling resistance, and durability by the following test methods, and the results are shown in Table 2. In Table 2, the structure A means the belt reinforcing layer shown in FIGS. 2 (a) to 2 (b), and the structure B means the belt reinforcing layer shown in FIGS. 3 (a) to 3 (b).

Road noise:
The test tire was mounted on a passenger car having a displacement of 2000 cc under a pressure of 200 kPa, and the in-vehicle noise [dB] when traveling on a rough road surface at a speed of 60 km / h was measured. The evaluation results are shown as an index with Comparative Example 3 as 100. It means that road noise is so small that this index value is small.

Rolling resistance:
The rolling resistance of the test tire was measured using an indoor drum type testing machine having a drum diameter of 1707 mm. The evaluation results are shown as an index with Comparative Example 3 as 100. It means that rolling resistance is so small that this index value is small.

durability:
After the end of the high-speed durability test specified in JIS D4230, the speed was further increased in units of 10 km / h every 30 minutes, and the running distance until the tire broke was measured. The evaluation results are shown as an index with Comparative Example 3 as 100. The larger the index value, the better the durability.

As shown in Table 2, the tire of Example 1 has the same durability as that of the tire of Comparative Example 3 in which nylon cords are used for the belt reinforcing layer, and also obtains an effect of reducing road noise and rolling resistance. I was able to. On the other hand, the durability of the tires of Comparative Examples 1 and 2 using a polyethylene terephthalate cord for the belt reinforcement layer was lower than that of the tire of Comparative Example 3.

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention. The specific structure of the belt reinforcement layer in this invention is shown, (a) is a schematic sectional drawing, (b) is a schematic plan view. The other structure (reference example) of a belt reinforcement layer is shown, (a) is a schematic sectional drawing, (b) is a schematic plan view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 7 Belt reinforcement layer 7A Center part 7B, 7C End part

Claims (2)

In a pneumatic radial tire in which a belt layer is disposed on the outer peripheral side of the carcass layer, and a belt reinforcing layer formed by winding a reinforcing cord in the tire circumferential direction is disposed on the outer peripheral side of the belt layer, as a reinforcing cord for the belt reinforcing layer , Rutotomoni using hybrid cord formed by twisting a fiber of the fiber and nylon polyketone, the belt reinforcing layer is divided into a central portion and both end portions in the tire width direction, a central portion of the belt reinforcing layer A pneumatic radial tire in which an aliphatic polyketone cord is disposed at both ends of the belt reinforcing layer while the hybrid cord is disposed . The pneumatic radial tire according to claim 1 , wherein the aliphatic polyketone has a structure represented by the following formula (1).
_{- (CH 2 -CH 2 -CO)} n- (R-CO) m- ··· (1)
Here, 1.05 ≧ (n + m) /n≧1.00, R is an alkylene group having 3 or more carbon atoms.

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