Shaft circulation ball screw

A shaft circulation ball screw, comprising:

• a screw provided with a screw helical groove and a return passage;
• a nut provided with an insertion hole for insertion of the screw, a nut helical groove being formed on an inner surface of the insertion hole to cooperate with the screw helical groove to form a load path for accommodation of a plurality of rolling elements;
• and
• a circulation member connected between two ends of the load path for circulation of the rolling elements and cooperating with the screw to form a return path;
• wherein the screw is provided with a stop portion for the two ends of the circulation member to rest against, a distance from the stop portion to a central axis of the screw is defined as a first height H, a distance from a highest point of the rolling elements which are located in the return passage to the central axis of the screw is defined as a second height Hmax, and Hmax satisfies the following relations:
• Hmax−0.5×BD≦H≦Hmax;
• Hmax=R1+(0.5×PCD−R1)xsin α;
• Hmax−0.5×BD≦H≦Hmax;
• and
• R1+(0.5×PCD−R1)xsin α−0.5×BD≦H≦R1+(0.5×PCD−R1)xsin α;
• R1 is a first return radius of curvature;
• R2 is a second return radius of curvature;
• PCD is a pitch diameter;
• BD is a diameter of the rolling elements;
• α is a lead angle.