Ball screw apparatus with wire coils

摘要

A ball screw apparatus includes a cylindrical screw shaft having a spiral groove in an outside peripheral surface, a cylindrical ball nut surrounding the screw shaft and having a spiral groove in an inside peripheral surface, and a plurality of bearing balls rotatably interposed the two spiral grooves, which are aligned and spaced apart such that the bearing balls are free to rotate as the ball nut rotates about and moves along the screw shaft. One or more of the screw shaft and the ball nut may include a spiral wire coil and a coil shape retention device. The opposed peripheral surfaces of adjacent coils of each spiral wire coil form the walls of one of the spiral grooves. Each coil shape retention device prevents the associated spiral wire coil from changing shape when the ball nut moves spirally relative to the screw shaft.