Characteristics of Oscillatory Ball Screws : 1st Report, Oscillatory Friction Torque of Preloaded Ball Screws with Shim Plates

Abstract

The present report is concerned with the friction torque of oscillatory balll screws for various oscillatory angles of the screw shaft. The effect of reduction of the oscillatory friction torque by the use of spacer balls and the influence of lubricant on the oscillatory friction torque are also discussed. The results may be summarized as follows : (1) The oscillatory friction torque exceeds normal friction torque in the region of oscillatory angles of 15°∼2880°. (2) The upper limit of the region agrees approximately with an angle corresponding to 2 times the number of thread turns of the ball nut. (3) The oscillatory friction torque has a maximum at an oscillatory angle of 360°. (4) The maximum value attains 2. I times the friction torque in normal operation. (5) Use of spacer balls is effective for reducing the oscillatory friction torque.