To provide a power transmission device, having a torque limit function of preventing unnecessary interruption of power transmission in normal operation and surely interrupting power transmission in case of abnormality.
A stopper member 32 is interposed between a hub 16 driven to rotate and a driving shaft 11 screw-engaged with the hub 16. The stopper member 32 abuts on the hub 15 to regulate the hub from spirally advancing in the fastening direction to the driving shaft 11. The stopper member 32 is deformed by transmission of excessive torque, thereby allowing the hub 16 to spirally advance in the fastening direction to the driving shaft 11. When the hub 16 spirally advances in the fastening direction, a part to which the power is input and a part screw-engaged with the driving shaft 11 in the hub 16 are relatively displaced in the direction along the central axis L of rotation. A part scheduled to break of the hub 16 is broken by the stress based on the relative displacement and the stress based on the transmission of excessive torque, thereby interrupting the transmission of power from the hub 16 to the driving shaft 11.
KAWAGUCHI MASAHIRO
OTA MASAKI
INOUE YOSHINORI
Makoto Onda