| 摘要 |
The invention controls irregular wear in the shoulder land portions and reduces the occurrence of cracking in the shoulder grooves of a pneumatic tire. To that end, the groove wall surface (17a) on the shoulder land portion (19) side of the shoulder groove (17) has an inclined surface consisting of a first inclined part (171) inclined toward the equatorial plane of the tire at an inclination angle θ1, which is constant along the circumference of the tire, and a second inclined part (172) further inclined from the first inclined part (171) toward the equatorial plane of the tire and reaching the groove bottom (17b) of the shoulder groove (17) at an angle α with respect to the first inclined part (171), which varies along the circumference of the tire. Also, the inclination angles of the first and second inclined parts (171, 172) are set such that the maximum value αmax and the minimum value αmin of the angle α satisfy (D−d) (tan αmax−tan αmin)≧2.5 where D is the depth from the tread face to the bottom of the shoulder groove (17), d is the depth from the tread face to the boundary position between the first inclined part (171) and the second inclined part (172), αmax is the maximum value of the angle α, and αmin is the minimum value of the angle α. |
| 主权项 |
1. A pneumatic tire comprising:
a tread having, on a surface thereof, a plurality of circumferential grooves, which extend along a circumference of the tire, and shoulder land portions defined by shoulder grooves, which are circumferential grooves located in axially outermost positions of the circumferential grooves, wherein a groove wall surface located on the shoulder land portion side of the shoulder groove has a first inclined part, which is inclined toward an equatorial plane of the tire from a direction perpendicular to a tread face of the shoulder land portion, and a second inclined part, which is further inclined toward the equatorial plane from the first inclined part and reaches a bottom of the shoulder groove, wherein an inclination angle of the first inclined part is constant along the circumference of the tire and an angle α formed by the first inclined part and the second inclined part varies along the circumference of the tire, and wherein a maximum value αmax and a minimum value αmin of the angle α satisfy (D−d)(tan αmax−tan αmin)≧2.5 mm,
where D is a depth from the tread face to the bottom of the shoulder groove,d is a depth from the tread face to a boundary position between the first inclined part and the second inclined part,αmax is a maximum value of the angle α, andαmin is a minimum value of the angle α, wherein the depth d satisfies 0.1<(d/D)<0.4, wherein the second inclined part has a plurality of groove-bottom sipes which are arranged along the circumference of the tire and open into the shoulder groove, wherein I and w satisfy 1.5<(I/w)<4 where w is a length of each groove-bottom sipe along the groove wall surface and I is an interval between an opening of a groove-bottom sipe and an opening of a groove-bottom sipe adjacent thereto along the circumference of the tire, and wherein the plurality of groove-bottom sipes is provided only in the second inclined part and wherein the shoulder land portions do not have land-portion sipes. |
