| 摘要 |
PROBLEM TO BE SOLVED: To improve wetting performance without impairing noise performance by forming a corner part for crossing a groove wall of a vertical groove and a groove wall of a horizontal groove as the conical surface having a radius of curvature gradually becoming large toward the grounding surface side from the groove bottom side. SOLUTION: To improve wetting performance without impairing noise performance, only a flow of water is smoothed in a corner part 5, and a flow of air is not smoothed. The corner part 5 for crossing a groove wall 3a of a vertical groove and groove wall 4a of a horizontal groove in a block B is constituted as the conical surface 6 having a radius of curvature gradually becoming large toward the grounding surface 7 side of the block B from the groove bottom 9 side. Here, a radius R of curvature of the corner part 5 can be decided by a cross section parallel to the grounding surface 7 of the block B. Here, in the corner part 5, a radius of curvature is substantially set to 0 in the groove bottom 9, and a radius of curvature in the grounding surface is particularly desirably set to 6 to 8 mm. |
