WORM GEAR

摘要

A worm gear capable of smoothly picking up balls from a ball returning raceway. The worm gear comprises a worm body (20) allowing balls (17) to roll on the outer periphery thereof and having a spiral worm groove (15a) formed therein, a wheel (16) meshing with the worm body (20) through the plurality of balls (17), a shaft (21) installed on the inside of the worm body (20) and forming the spiral ball returning raceway ß between the shaft and the inside of the worm body (20), a circulation member (22) having, therein, a connection raceway ? connecting the worm groove (15a) to the ball returning raceway ß, and the plurality of balls (17) arranged in a circulation route formed of the spiral worm groove raceway a, the ball returning raceway ß, the connection raceway ? along the worm groove (15a). Also, a bilge-shaped picking part (22b) in which a groove (36) gradually narrowed toward the bottom of the connection raceway ? is formed at the end part of the circulation member (22) on the ball returning raceway ß side. The balls (17) moving in the ball returning raceway ß are led to the bottom side of the connection raceway ? while being held by both sides (38) of the bilge-shaped picking part (22b).