The Yokohama Rubber Co., Ltd.

Satoru Isobe

Nobuo Suzuki

Kazuyuki Kabe

Yukihito Yamaguchi

Hirokatsu Maruyama

Hironori Kobayashi

Lisa Tauchi

When a tire that is mounted on a specified rim, inflated to an internal pressure of 50 kPa, and placed in a no-load state is viewed as a cross-section from the tire meridian direction, a position of 1.30&#xd7;Hf on an outer surface of a sidewall portion, taking a rim flange height (Hf) of the specified rim as a reference, is defined as a point (P), a foot of a normal line (L) drawn from the point (P) to a carcass line of a main body portion () of a carcass layer () is defined as a point (M), and a point of intersection of the normal line (L) and a carcass line of a folded back portion () of the carcass layer () is defined as a point (T). At this time, a distance (a) mm from the point (M) to the point (T), a distance (b) mm from the point (T) to the point (P), and a specified load (x) kN have relationships such that a=0.019&#xd7;x+13.3 and b=0.052&#xd7;x+21.6, with a tolerance of not less than 0% and not more than 20%.

Pneumatic tire

This pneumatic tire () includes: a pair of bead cores (); a carcass layer () extending between the pair of bead cores (); and a belt layer () including a laminate of at least four belt plies (to) having steel belt cords covered with coating rubber, the belt layer being disposed on the outer side in a tire radial direction of the carcass layer (). An inter-cord distance (Ga) between an outermost layer belt ply (fourth belt ()) and an adjacent belt ply (third belt ()) has a relationship such that 0.80&#x2264;Ga/&#x3c6;max&#x2264;1.80 with respect to a maximum value (&#x3c6;max) of outer diameters (&#x3c6;) of belt cords () in the outermost layer belt ply () and the adjacent belt ply ().

A pneumatic tire includes two cross belts having codes forming 5 to 30 degrees to a tire circumferential direction; a circumferential reinforcing layer having a width smaller than the cross belts, and having codes forming 0 to 5 degrees to the tire circumferential direction; and a carcass located inside, in a tire diameter direction, relative to a cross belt being inside among the cross belts. At 100% internal inflation pressure, a distance Xbetween an equatorial plane and an outer edge of the circumferential reinforcing layer is 60% to 75% of a distance W between the equatorial plane and an outermost section of the carcass, and at 5% internal inflation pressure, a distance Y between the equatorial plane and a separation section of the carcass and a belt outwardly adjoining the carcass is 95% to 105% of a distance Xbetween the equatorial plane and the outer edge.

In a pneumatic tire for heavy load including a circumferentially-formed groove running in a tire circumferential direction on a surface of a tread part, when a pneumatic pressure equivalent to a normal inner pressure is applied with reference to a case where a pneumatic pressure equivalent to an inner pressure of kPa is applied, a radius growth in a tire radial direction at a crown center of the tread part and in the circumferentially-formed groove located at the most lateral side in a tire width direction is made to be less than 0.3%.

Pneumatic tire for heavy load

The present invention provides a pneumatic tire that inhibits any fatigue rupture at an edge portion of a circumferential-direction reinforcing belt layer and also inhibits any separation at an edge portion of crossed belt layers. In the pneumatic tire, at least two crossed belt layers are disposed on the outer circumferential side of a carcass layer in a tread portion. At least one circumferential-direction reinforcing belt layer with a width smaller than those of the crossed belt layers is disposed between the crossed belt layers. Moreover, a stress relaxation layer of a rubber composition having a fixed thickness is disposed between the crossed belt layers while lying adjacent to an edge portion of and outside, in the width directions of, the circumferential-direction reinforcing belt layer.

In a pneumatic tire, 48%&#x2266;HB/HA&#x2266;52%, 98%&#x2266;HC/HA&#x2266;100%, 108%&#x2266;WB/WA&#x2266;115%, and 55%&#x2266;WC/WA&#x2266;75% are satisfied, where, when a line from a position A of rim height FH in tire width direction is X-axis and a line in tire radial direction via center crown CL is Y-axis, WA is distance of a half of tire base width, WB is distance from the Y-axis to a maximum width position P of a carcass layer, WC is distance from the Y-axis to an inflection point Q of the carcass layer, HA is distance from the X-axis to a peak R of the carcass layer on the center crown CL, HB is distance from the X-axis to the maximum width position P, and HC is distance from the X-axis to the inflection point Q.

In a pneumatic tire, a belt layer includes six superposed belt members. The edge of the fourth belt member on the tire-width direction outer side and the edge of the sixth belt member on the tire-width direction outer side are at approximately the same position in a tire width direction.

Growing community of inventors

Hiratsuka, Japan

Satoru Isobe