Bridgestone Corporation

Masakazu Amano

Takayuki Kurata

Shinsaku Katayama

Ataka Takei

Yoshio Kaji

Masafumi Koide

Eisuke Seta

Hiroyuki Katsuno

Satoshi Ishikawa

Koichi Ota

Yoshikage Sato

Masahiro Yabashi

By forming a ground contact edge side of lug grooves such that the groove depth becomes shallower in groove depth from the tire equatorial plane side toward the ground contact edge, and by setting an average angle of inclination formed between a tread face and a groove bottom to be not more than 5&#xb0;, water expulsion is performed smoothly in the vicinity of the ground contact edge while securing the rigidity of land portions in the vicinity of the ground contact edge. This enables a high degree of both wet performance and dry performance to be achieved.

Pneumatic tire

A pneumatic tire (), which has, in the surface of the tread (), lug grooves () on one side extending from one axial edge towards the axial center of the tire in such a manner as to intersect with the circumferential direction of the tire and lug grooves () on the other side extending in a symmetrically opposite direction from the axial center towards the other axial edge of the tire, has at least one circumferential groove () extending circumferentially around the tire. Also, circumferential grooves () are so formed as to satisfy a relationship of '1&#x2264;(S/L)&#x2264;3' where L is the axial length of the central region, which is the region enclosed by two straight parallel lines each passing through the center between the contact width center (CL) and the contact edge with the shoulder regions being the regions axially outside of the parallel lines, and S is the total of the groove areas of the circumferential grooves () disposed in the central region. Therefore, the pneumatic tire () not only secures the steering stability performance on wet road surfaces, but also improves the steering stability and wear resistance performance on dry road surfaces.

Pneumatic tire having lug grooves forming a direction tread pattern

Disclosed is a tire () which comprises: a bead core (); a first bead filler (); a first carcass (); a second bead filler (); and a rubber chafer () disposed at the outer side of the second bead filler () in the tread width direction. The second bead filler () covers a first bead filler outer end part () in the tread width direction, and a second bead filler inner end part () is disposed outside the bead core () in the tire radius direction. The rubber chafer () covers the second bead filler () in the tread width direction, and the loss tangent of the second bead filler () is smaller than the loss tangent of the rubber chafer ().

Tire

A pneumatic tire () has, in the surface of the tread (), a central circumferential groove () located at the center of the contact patch width and extending circumferentially around the tire, a plurality of longitudinal grooves (()) formed on the axially outside of the central circumferential groove (), lug grooves (), and blocks ((to)) defined by the central circumferential groove (), the longitudinal grooves (), and the lug grooves (). Each of the lug grooves () is formed such that its width in the shoulder region is greater than its width in the central region, and the sum of the groove area of the central circumferential groove () and the groove area of the longitudinal grooves () is smaller than the area of the lug grooves (). As a result, the pneumatic tire () not only secures the wet braking performance and wear resistance performance on paved roads, but also improves the acceleration performance and braking performance and the steering stability performance on snowy roads.

High wet braking performance is obtained without causing deterioration to other aspects of performance. Circumferential direction groovesare configured with first groove portionsof zigzag shape formed at the road surface side and second groove portionsof straight line shape formed at the groove bottom side. Accordingly, an effect (edge effect) is effectively exhibited by the edges of the first groove portionscatching on the road surface when running on a comparatively shallow water depth. High wet braking performance is accordingly obtained. Water in the grooves flows smoothly due to the presence of the second groove portionsat the groove bottom side when running on a comparatively deep water depth. Reliable ground contact performance of the tread surface of the treadto the road surface and high wet braking performance is accordingly obtained. High wet braking performance can be secured irrespective of whether there is shallow or deep water due to the edge effect of the first groove portionsand due to the water expelling effect of the second groove portions

Pneumatic tire with tread having circumferential grooves

A tire of the present invention has a roughness motif maximum length A in a predetermined range on at least a part of the tread surface. In addition, a tire forming mold of the present invention has a roughness motif maximum length A in a predetermined range on at least a part of the tread-surface molding surface.

Growing community of inventors

Kodaira, Japan

Masakazu Amano