Heavy load radial tire

Abstract

A belt layer 7 of a heavy load radial tire includes second and third belt plies 7B and 7C in which belt cords are arranged at an angle in a range of 10 to 45° with respect to a circumferential direction of the tire, and a fourth belt ply 7D which is disposed outside of the second and third belt plies 7B and 7C and which is spirally wound in the circumferential direction of the tire. When ply widths of the belt plies 7B to 7D are defined as W2 to W4 and at read ground-contact width is defined as Tw, the following relations are established: 0.85Tw≦W2, 0.85Tw≦W3, (W2−W3)≧14 mm, W4≧40 mm. A distance K between a tire equator and an outer end of the fourth belt ply 7D is in a range of 35% to 40% of the tread ground-contact width Tw. A reinforcing rubber layer 10 having the maximum thickness T1 of not less than 3.0 mm and a complex elastic modulus E* of in a range of 6.0 to 12.0 MPa is disposed between outer ends of the second and third belt plies 7B and 7C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing one embodiment of a heavy load radial tire of the present invention;

FIG. 2 is an enlarged sectional view of a tread portion of the tire;

FIG. 3 is a diagram used for explaining arrangement of cords of belt plies;

FIG. 4 is a diagram used for explaining arrangement of cords of belt plies of another embodiment; and

FIG. 5 is a diagram used for explaining arrangement of cords of belt plies of a conventional tire.

Claims

1. A heavy load radial tire comprising a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a belt layer disposed radially outward of the carcass and in the tread portion, wherein the belt layer includes a second belt ply in which belt cords are arranged at an angle θ2 of 10 to 45° with respect to a circumferential direction of the tire,a third belt ply which is disposed radially outward of the second belt ply, in which belt cords are arranged at an angle of θ3 of 10 to 45° with respect to the circumferential direction of the tire and an inclining direction of the belt cords of the third belt ply is opposite from that of the belt cords of the second belt ply, anda fourth belt ply which is disposed radially outward of the third belt ply, in which a belt cord is spirally wound at an angle θ4 of not more than 5° with respect to the circumferential direction of the tire, whereinply widths W2 and W3 of the second and third belt plies in an axial direction of the tire are not less than 85% of a tread ground-contact width Tw,a ply width W4 of the fourth belt ply in the axial direction of the tire is not less than 40 mm, a distance K between an outer end of the fourth belt ply in the axial direction of the tire to a tire equator is in a range of 35% to 40% of the tread ground-contact width Tw,a difference W2−W3 of the ply widths W2 and W3 of the second and third belt plies in the axial direction of the tire is not less than 14 mm,a reinforcing rubber layer is disposed between outer ends of the second and third belt plies in the axial direction of the tire, a maximum thickness T1 of the reinforcing rubber layer is not less than 3.0 mm, and a complex elastic modulus E*1 of the reinforcing rubber layer is in a range of 6.0 to 12.0 MPa.

2. The heavy load radial tire according to claim 1, wherein the fourth belt ply is disposed at a distance from both sides of the tire equator.

3. The heavy load radial tire according to claim 2, wherein the belt layer includes a fifth belt ply above the tire equator and between a pair of the fourth belt plies, belt cords of the fifth belt ply are inclined at an angle θ5 of 10 to 45° with respect to the circumferential direction of the tire and in the same inclination direction as that of the belt cords of the third belt ply.

4. The heavy load radial tire according to claim 1, wherein the belt layer includes a first belt ply on the radially innermost side, belt cords of the first belt ply are inclined at an angle θ1 that is greater than the angle θ2 and in a range of 45 to 75° with respect to the circumferential direction of the tire.

5. The heavy load radial tire according to claim 1, wherein the reinforcing rubber layer has a maximum thickness T1 in an outer end of the third belt ply in the axial direction of the tire.

6. The heavy load radial tire according to claim 1, wherein an axially outer end portion of the belt layer is gradually separating from the carcass axially outward of the tire, a cushion rubber is disposed in this separating portion, a complex elastic modulus E*2 of the cushion rubber is in a range of 2.0 to 5.0 Mpa and is smaller than the complex elastic modulus E*1 of the reinforcing rubber layer.

7. The heavy load radial tire according to claim 6, wherein the cushion rubber includes a sheet-like auxiliary layer portion extending between the belt layer and the carcass to the tire equator, the auxiliary layer portion has a thickness of 0.5 to 2.0 m.

8. The heavy load radial tire according to claim 1, wherein a tread rubber includes a base rubber which is adjacent to the belt layer, and a cap rubber forming a tread surface, the complex elastic modulus E*1 of the reinforcing rubber layer is greater than a complex elastic modulus E*3 of the base rubber.

9. The heavy load radial tire according to claim 2, wherein the reinforcing rubber layer has a maximum thickness T1 in an outer end of the third belt ply in the axial direction of the tire.

10. The heavy load radial tire according to claim 3, wherein the reinforcing rubber layer has a maximum thickness T1 in an outer end of the third belt ply in the axial direction of the tire.