| 摘要 |
A pneumatic tire sufficiently enhances the frequency dispersion effect for the columnar resonance noise due to the presence of the circumferential grooves, per se, or the lowering effect for the sound pressure level, in association with the cross-sectional area of the lateral grooves. The tire has a tread surface provided with a plurality of circumferential grooves (2, 4) extending continuously in a circumferential direction. The circumferential grooves (2, 4) are each provided with a plurality of lateral grooves (7, 8) each having one end opened into that circumferential groove and the other end terminating in a land portion (7, 8), independently from other circumferential grooves, other lateral grooves opening into said other circumferential grooves or in a ground contacting end of a tread. The circumferential grooves (2, 4) and the lateral grooves (7, 8) each has a groove widths determined such that their opposite groove walls do not contact each other under a tire posture wherein the tire is mounted onto an approved rim, filled with the maximum air pressure and loaded with a mass that corresponds to the maximum load capacity of the tire. The lateral grooves are arranged so that at least one lateral groove is always included completely in the ground contact surface of the tread. The groove width of the lateral grooves is at least locally not less than 30% of the groove width of the circumferential grooves. Each lateral groove has an extending length which is not less than 40% of an extending length of said circumferential grooves in said ground contact surface. Each lateral groove (7, 8) is provided with a region having a cross-sectional area which increases from its side of opening end into the circumferential groove (2, 4) toward its side of the terminal end, and including a starting end with a minimum cross-sectional area point (A) that is situated closer to the circumferential groove 2, 4 in which the lateral groove (7, 8) opens, than a maximum cross-sectional area point (B) at the terminal end of the increasing cross-sectional area region. |
