Pneumatic tire with tread having three dimensional sipes
A pneumatic tire comprises a tread block having a top face provided with a three-dimensional sipe, the sipe extending along its longitudinal direction with an angle of 0 to 45 degrees with respect to a tire axial direction, the sipe having a first opening configuration extending in a wavy manner with amplitude W and a cycle a1 in a cross sectional view of the block parallel to the top face, the sipe having a second opening configuration extending in a wavy manner with amplitude W and a cycle a2 in a cross sectional view of the block perpendicular to the longitudinal direction of the sipe, and the sipe satisfying the following relation (1) in a rectangular coordinate system in which the x-axis corresponds to the longitudinal direction, the z-axis corresponds to a depth direction of the sipe: y=W ·sin {(2π· x/a 1)+(2π· z/a 2)+θ}.
1. A pneumatic tire comprising
a tread portion having a plurality of blocks comprising a first block and a second block, said first block having a top face provided with a first three-dimensional sipe, said second block having a top face provided with a second three dimensional sipe,
each of said first and second three-dimensional sipes extending along its longitudinal direction having an angle α in a range of from 0 to 45 degrees with respect to an axial direction of the tire,
each of said three dimensional sipes having a first opening configuration that extends in a wavy manner having amplitude W and a cycle a1 in a cross sectional view of said block being parallel to the top face,
each of said first and second three dimensional sipes having a second opening configuration that extends in a wavy manner having amplitude W and a cycle a2 in a cross sectional view of said block being perpendicular to the longitudinal direction, and
each of said first and second three dimensional sipes satisfying the following relation in a rectangular coordinate system of x, y, z axes in which the x-axis corresponds to the longitudinal direction of each sipe, the z-axis corresponds to a depth direction of each sipe, and the y-axis is perpendicular to the x and y axes:
y=W ·sin {(2π· x/a 1)+( 2 π· z/a 2)},
wherein said first block has a maximum axial block width in said blocks and said second block has a minimum axial block width in said blocks,
the first three dimensional sipe of the first block has the cycle a2 larger than the cycle a2 of the second three dimensional sipe of the second block,
the first and second three dimensional sipes differ from each other with respect to the cycle a2, and
the first and second three dimensional sipes have the same cycle a1 and amplitude W.
2. The tire according to claim 1 , wherein the cycle a1 of the first opening configuration of each of said first and second three dimensional sipes is in a range of from 14% to 90% of a length BL of said block measured along the x-axis.
3. The tire according to claim 1 , wherein the cycle a2 of the second opening configuration of each of said first and second three dimensional sipes is in a range of from 14% to 90% of a height BH of said block measured along the z-axis.