| 摘要 |
PROBLEM TO BE SOLVED: To materialize a structure which is easy both to secure reliability and durability and to reduce size and weight by increasing breaking strength when large load is applied.SOLUTION: A basal end outer peripheral surface of each shaft 14 constituting a cross spider 11a and a stepped surface 30 serving as an external face of a coupling base 15 are connected via concaved planes 31a whose cross sections are partially arcuate, respectively. A radius of curvature of the cross section of these concaved planes 31a is made larger on the side of a distal half 33 connecting with an outer peripheral surface of each shaft 14 and made smaller on the side of a basal half 32 connecting with the stepped surface 30. With such a constitution, the radius of curvature R of the cross section of a part in the concaved planes 31a where stress occurring when transmitting torque is likely to increase is made to be large, thereby making damage such as cracks hard to occur on the basal end of each shaft 14, without unnecessarily enlarging a longitudinal dimension of each shaft 14. |
