Pneumatic Radial Tire

• US 20080135152A1
• Filed: 01/20/2006
• Published: 06/12/2008
• Est. Priority Date: 01/21/2005
• Status: Active Grant

• Current Assignee: Bridgestone Corporation
• Original Assignee: Bridgestone Corporation
• Inventors: Nakajima, Daisuke
• Granted Patent: US 7,823,616 B2
• Time in Patent Office: Days
• US Class Current: 152/458
• CPC Class Codes: B60C 9/0042 Reinforcements made of synthetic materials
• CPC Class Codes: B60C 9/20 built-up from rubberised plies each having all cords arranged substantially parallel
• CPC Class Codes: D02G 3/48 Tyre cords tyre reinforcements B60C9/00; metal cords for reinforcing rubber or plastic articles D07B1/0606
• CPC Class Codes: Y10T 152/10513 Tire reinforcement material characterized by short length fibers or the like
• CPC Class Codes: Y10T 152/10783 Reinforcing plies made up from wound narrow ribbons
• CPC Class Codes: Y10T 428/2967 Synthetic resin or polymer

Abstract

This invention relates to a pneumatic radial tire being excellent in steering stabilities during low-speed running and high-speed running, and more particularly to a pneumatic radial tire comprising at least one belt reinforcing layer 6A, 6B disposed on a belt 5 outward in a radial direction of the tire, characterized in that a reinforcing element constituting the belt reinforcing layer 6A, 6B is a polyketone fiber cord satisfying conditions of the following equations (I) and (II):

σ≧−0.01×E+1.2   (I)

σ≧−0.02   (II)

[wherein σ is a thermal shrinkage stress (cN/dtex) at 177° C.; and E is an elastic modulus (cN/dtex) at 25° C. under a load of 49 N].

Claims

1. A pneumatic radial tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion continuing to both the sidewall portions, a carcass toroidally extending between the pair of bead portions, a belt disposed on a crown portion of the carcass outward in a radial direction of the tire and comprised of at least two belt layers, and at least one belt reinforcing layer disposed on the belt outward in the radial direction of the tire so as to cover a whole and/or both end portions of the belt and composed of a rubberized layer containing reinforcing elements substantially arranged in parallel to the circumferential direction of the tire, characterized in that the reinforcing element constituting the belt reinforcing layer is a polyketone fiber cord satisfying conditions of the following equations (I) and (II):

σ

≧

−

0.01×

E+1.2 

 

(I)

σ

≧

−

0.02 

 

(II)

[wherein σ

is a thermal shrinkage stress (cN/dtex) at 177°

C.; and

E is an elastic modulus (cN/dtex) at 25°

C. under a load of 49 N].

2. A pneumatic radial tire according to claim 1, wherein an end count of the polyketone fiber cords in the belt reinforcing layer is 40 to 70 (cords/50 mm).

3. A pneumatic radial tire according to claim 1, wherein the belt reinforcing layer is formed by spirally winding a rubberized strip-shaped sheet containing one or more reinforcing elements and having a width narrower than that of the belt reinforcing layer plural times in a widthwise direction of the tire so as to have a predetermined width.

4. A pneumatic radial tire according to claim 1, wherein the polyketone fiber cord used in the belt reinforcing layer is formed by twisting two filament bundles of polyketone.

5. A pneumatic radial tire according to claim 4, wherein the polyketone fiber cord used in the belt reinforcing layer has a twisting coefficient α

of 850 to 4000 defined by the following equation (III);

α

=T×

D^1/2 

 

(III)

[wherein T is a twisting number (times/100 mm), and D is a total fineness (dtex) of the cord].

6. A pneumatic radial tire according to claim 4, wherein the polyketone fiber cord used in the belt reinforcing layer is formed by twisting two filament bundles of polyketone having a fineness of 500 to 3000 dtex.

7. A pneumatic radial tire according to claim 1, wherein the polyketone fiber cord used in the belt reinforcing layer is formed by twisting one filament bundle of polyketone.

8. A pneumatic radial tire according to claim 7, wherein the polyketone fiber cord used in the belt reinforcing layer has a twisting coefficient α

of 300 to 1300 defined by the following equation (III);

α

=T×

D^1/2 

 

(III)

[wherein T is a twisting number (times/100 mm), and D is a total fineness (dtex) of the cord].

9. A pneumatic radial tire according to claim 7, wherein the polyketone fiber cord used in the belt reinforcing layer is formed by twisting one filament bundle of polyketone having a fineness of 500 to 3000 dtex.

10. A pneumatic radial tire according to claim 1, wherein the polyketone substantially has a repeating unit represented by the following general formula (IV):

[wherein A is a moiety derived from unsaturated compounds polymerized with unsaturated bonds, and may be same or different in each of repeating units].

11. A pneumatic radial tire according to claim 10, wherein A in the formula (IV) is ethylene group.

12. A pneumatic radial tire according to claim 1, wherein the polyketone fiber cord has a reversibility of shrinking at an elevated temperature and stretching in the turning to room temperature.