Patent ID: 8167493
Filing Date: 2012-05-01
Classification: F16C

Abstract:
1. A ball spline comprising: a spline shaft having a substantially circular sectional configuration, and having in the outer peripheral surface thereof a plurality of lines of longitudinally extending arcuate torque transmission grooves arranged at equal intervals, with the ball rolling faces being formed on side surfaces of land parts situated in between the torque transmission grooves, such that the ball rolling faces are on both sides in the width direction of each torque transmission groove; and a spline nut formed substantially as a cylinder with a hollow hole into which the spline shaft is fitted, having on an inner peripheral surface of the hollow hole a plurality of lines of load rolling faces which are adjacent in the circumferential direction opposed to the ball rolling faces of the spline shaft; a large number of balls rolling while receiving a load in the load region formed whereby the ball rolling faces of the spline shaft and the load rolling faces of the spline nut are opposed to each other; and the distance between a pair of rows of balls rolling on the ball rolling faces situated on both sides of each of the land parts is set larger than the distance between a pair of rows of balls rolling on the ball rolling faces on both sides of each of the torque transmission grooves, the spline nut has ball return passages which are formed parallel to the load regions, and are situated in the contact normals (n) of the balls and the ball rolling faces, the spline nut has first ball retaining portions, formed of synthetic resin, which are protruded from the inner peripheral surface of the spline nut, each of the first ball retaining portions is accommodated in the torque transmission groove, and is disposed between a pair of rows of balls rolling on the ball rolling faces on both sides of each of the torque transmission grooves, the spline nut is equipped with an endless circulation path for the balls rolling on the load rolling faces; and a pair of endless circulation paths situated on both sides of each torque transmission groove of the spline shaft cross each other so that one endless circulation path passes through an inside of another endless circulation path.