Ball spline having reinforcement bush part

A ball spline (100) having a reinforcement bush part, comprising:

• a rod-shaped spline shaft (110) having at least one concave track groove (111) formed to extend in the longitudinal direction thereof;
• a nut part in which the spline shaft (110) is inserted so that the nut part can move in the longitudinal direction of the spline shaft;
• and
• a plurality of balls (150) provided between the nut part and the spline shaft (110) so as to circulate,
• wherein:
• the nut part includes a nut (120) which is a hollow body into which the spline shaft (110) is inserted, and retainers (130), which are hollow bodies provided at both sides of the nut (120) in the longitudinal direction of the nut (120) and into which the spline shaft (110) is inserted;
• the nut part is provided with at least one spline part;
• the spline part includes a concave load track groove (125), which is formed in the longitudinal direction on the inner surface part (121) of the nut (120) so as to face the track groove (111), a no-load circulation part (127) formed in parallel to the load track groove (125) in the longitudinal direction, and a curved concave spline circulation groove (133), which is formed in each of the retainers (130) and has one side facing the end portion of the load track groove (125) and the other side facing the end portion of the no-load circulation part (127);
• some of the balls (150) are diverted in spline circulation grooves (133) of the retainers (130) which are provided on both sides in the longitudinal direction and circulate and move between the track groove (111) and the load track groove (125) and along the no-load circulation part (127);
• the nut part further includes at least one reinforcement bush part in parallel with the spline part;
• and
• the others of the balls (150) rolls in contact with the outer surface of the spline shaft (110) and circulate and move along the reinforcement bush part.