Patent ID: 6892775
Filing Date: 2005-05-17
Classification: B60C,Y10S

Abstract:
1. In a pneumatic radial tire for all-season passenger car comprising: a tread with a tread pattern defined by dividing the tread into many blocks through a plurality of slant grooves arranged at given intervals in a circumferential direction of the tire and at least one circumferential center groove extending in the circumferential direction of the tire at a center portion of the pattern, and consisting of a central zone having a width corresponding to 30-60% of a tread width and a pair of side zones located on both sides of the central zone; wherein (1) the slant grooves comprise steeply slant grooves extending at a relatively small inclination angle with respect to the circumferential direction and gently slant grooves extending at a relatively large inclination angle with respect to the circumferential direction; (2) the steeply slant grooves are opened to the circumferential center groove in the central zone of the tread, while the gently slant grooves are opened to a tread end in each of said side zones of the tread to form blocks in said side zones; (3) the number of the gently slant grooves is made two or more times than the number of the steeply slant grooves so that an interval between the gently slant grooves in the circumferential direction is made ½ or less than an interval between the steeply slant grooves in the circumferential direction; (4) each of the blocks is provided with at least one sipe; and (5) blocks formed in the central zone are defined by the circumferential center groove and the steeply slant grooves and are chamfered from a tapered top end over a range of 10-30 mm in a longitudinal direction of the block so as to gradually shallow a depth of a surface of the block from the tapered top end toward an opposite end of the block; and wherein the block formed in the central zone of the tread has at least two sipes, each opening to a steeply slant groove at a cross angle of not less than 45°, and said at least two sipes are arranged and configured so as to divide the block into first, second and third tread elements, wherein the first tread element is generally arrow-shaped with a head portion comprising the chamfered tapered top end and a rear portion separating the second and third tread elements.