| 摘要 |
PROBLEM TO BE SOLVED: To prevent damage of bristles in a brush shield by setting a clearance between the brush shield and one shield tooth closest to the brush shield to be larger than that between a pair of shield teeth closest to the brush shield. SOLUTION: In a longitudinal upstream side part 24 of a radial inner side 22, a plurality of shield teeth 28, 30 spaced mutually in the longitudinal direction and extended in the circumference direction so as protrude inward radially are formed. The radial inner side 22 has a longitudinally variable radius, that is, a line vertically extending from a longitudinal axis line 21 to the radial inner side 22. This radius is increased longitudinally between a brush shield 38 and one shield teeth 28 longitudinally closest to the brush shield 38 to be larger than that between a pair of shield teeth 28, 30 longitudinally closest to the brush shield 38. In this way, damage of bristles 40 in the brush shield 38 can be prevented. |
