Patent ID: 7377194

Claim:
A worm gear mechanism comprising: a driving worm; a torque-transmitting worm wheel meshing with said worm for transmitting torque from said worm to a load side; an auxiliary worm wheel meshing with said worm and having a pitch diameter greater than a pitch diameter of said torque-transmitting worm wheel; and a resilient member for resiliently urging said auxiliary worm wheel relative to said torque-transmitting worm wheel, wherein, at positions where said torque-transmitting worm wheel and said auxiliary worni wheel mesh with said worm, a tooth of said worm is held at opposite surfaces thereof between teeth of said torque-transmitting worm wheel and said auxiliary worm wheel, and wherein said resilient member resiliently urges said auxiliary worm wheel in such a direction as to keep the tooth of said worm held between the teeth, wherein a pitch diameter of said worm defined when said auxiliary worm wheel is meshing with said worm is smaller than a pitch diameter of said worm defined when said torque transmitting worm wheel is meshing with said worm.