Patent ID: 7244214

Claim:
A speed change device comprising: an input member that is rotatable in opposite directions from a normal position within limited rotation angles, said input member transmitting higher torque as a rotation angle thereof, with respect to the normal position, becomes larger; an output member; and a variable angle-ratio change mechanism including rollers and teethed wheels that are arranged in parallel to each other and capable of transmitting torque between said input and output members, said rollers being capable of changing a speed ratio between said input member and said output member, and said teethed wheels being capable of changing a speed ratio between said input and output members; wherein said rollers and said teethed wheels are respectively connected to rotate together with each other; said teethed wheels being provided with teeth that have a clearance on a pitch circle of said teethed wheels between adjacent teeth thereof, the clearance being set larger than a slip amount of said rollers in a low torque range where said rollers transmit low torque between said input and output members with said teethed wheels being bypassed in a normal operation; and said teethed wheels being engageable with each other to transmit high torque between said input and output members in a high torque range where the high torque is applied between said input and output members in an exceptional operation and said rollers slip larger than the slip amount in the low torque range.