Heavy duty tire

Abstract

The heavy duty tire comprises a belt layer 7 comprised of at least three belt plies outside of a carcass 6 in a radial direction. Belt cords of a first belt ply 7A disposed innermost in the radial direction incline at an angle of 45 to 55 degrees with respect to a tire equator C. Belt cords of second and third belt plies 7B, 7C disposed outside thereof incline at an angle of 16 to 22 degrees with respect to the tire equator C and into mutually opposite directions. Width BW3 of the third belt ply 7C is smaller than width BW2 of the second belt ply 7B and is also 77 to 95% of a tread grounding width TW. Width BW1 of the first belt ply 7A is smaller than the width BW3 of the third belt ply 7C by 20 to 35 mm. An inter-cord distance S between the first belt ply 7A and the carcass ply 6A in the tire radial direction is 0.8 to 1.2 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a tire according to one embodiment of the present invention;

FIG. 2 is a partial enlarged view of a tread portion thereof;

FIG. 3 is an exploded view of a belt layer showing alignment of belt cords;

FIG. 4 is a partial sectional view along A-A in FIG. 2; and

FIG. 5 is a partial sectional view of a tread portion of a conventional heavy duty tire.

Claims

1. A heavy duty tire comprising a carcass that extends from a tread portion over sidewall portions up to bead cores of bead portions, and a belt layer that is disposed outside of the carcass in the tire radial direction and inward of the tread portion, wherein the carcass is comprised of a single carcass ply in which carcass cords made of steel cords are aligned in a radial direction,wherein the belt layer is comprised of at least three belt plies in which belt cords made of steel cords are aligned,the at least three belt plies includinga first belt ply disposed on a radially innermost side with the belt cords being inclined at an angle (θ1) of 45 to 55 degrees with respect to a tire equator,a second belt ply disposed radially outside thereof with the belt cords being inclined at an angle (θ2) of 16 to 22 degrees with respect to the tire equator, anda third belt ply disposed radially outside thereof with the belt cords being inclined at an angle (θ3) of 16 to 22 degrees with respect to the tire equator and also inclined in a direction opposite to that of the belt cords of the second belt ply,wherein the third belt ply has a width (BW3) corresponding to 77 to 95% of a tread grounding width (TW),the second belt ply has a width (BW2) that is larger than the width of the third belt ply (BW3), andthe first belt ply has a width (BW1) that is smaller than the width of the third belt ply (BW3) by 20 to 35 mm, andwherein an inter-cord distance (S) in the tire radial direction between the first belt ply and the carcass ply on the tire equator is 0.8 to 1.2 mm.

2. The heavy duty tire as claimed in claim 1, wherein the width of the second belt ply (BW2) is larger than the width of the third belt ply (BW3) by 10 to 20 mm.

3. The heavy duty tire as claimed in claim 1, wherein an insulation rubber having a complex elastic modulus of 6 to 9 MPa is disposed between the first belt ply and the carcass ply.

4. The heavy duty tire as claimed in claim 1, wherein the direction of inclination of the belt cords of the first belt ply with respect to the tire equator C is different from the direction of inclination of the belt cords of the second belt ply with respect to the tire equator C.

5. The heavy duty tire as claimed in claim 3, wherein the insulation rubber has a uniform thickness.

6. The heavy duty tire as claimed in claim 3, wherein a piece of cushion rubber is disposed between an outer end portion of the belt layer in a tire axial direction and the carcass, the cushion rubber having a maximum thickness at axially outer end of the second belt ply 7B and assuming a substantially triangular shaped section in which the thickness reduces from the maximum width position towards in and outside in the tire axial direction, and wherein the insulation rubber contacts an outer surface of the carcass and extends to both sides in the tire axial direction, both axially outer ends of the insulation rubber being located further outward in the tire axial direction than the axially outer ends of the cushion rubber.

7. The heavy duty tire as claimed in claim 6, wherein an axially inner end of the cushion rubber is located between the axially outer end of the first belt ply 7A and the tire equator C.