| 摘要 |
PURPOSE:To attempt the prevention of a groove bottom crack and the improvement of heat dissipation of a groove bottom and anti-stone seizure by making a tapered groove by inclining predeterminedly the groove wall of a tread groove and making a groove bottom partially circular with a predetermined radius of curvature and connecting the wall and the bottom with a predetermined circular arc section. CONSTITUTION:A treat groove 1 is formed into a tapered groove whose groove side wall 3 has a groove angle alpha of 5 deg.-35 deg., and a partially circular groove bottom portion 4 having the radius of curvature R which is 1/5-1/2 of a groove width W, is provided. And the groove wall 3 and the groove bottom portion 4 are connected at a circular arc connecting portion 6. A crossing point b where the extended line A of the groove wall 3 at a cross sectional surface vertical against the axis of the tread groove 1, crosses the extended circular arc B of the groove bottom portion 4, is sought, and this connecting portion 6 is formed with a circular arc which is convex toward the inside of a groove with the radius of curvature R' which comes into contact respective ly with a straight line ab and the groove bottom portion 4 from the outside. As a result, a groove bottom crack is prevented and the heat dissipating performance of the groove bottom and the performance of anti stone seizing can be improved. |
