Internal circulation ball screw

An internal circulation ball screw comprising:

• a threaded shaft having a first threaded groove and an imaginary axis;
• a nut sleeved onto the threaded shaft and having a second threaded groove and a receiving space, the second threaded groove corresponding to and fitting the first threaded groove, the receiving space having a first side and a second side, the second threaded groove intersecting the receiving space to form a first fracture and a third fracture at the first side and form a second fracture and a fourth fracture at the second side;
• a circulation member mounted to the receiving space and having a first circulation channel and a second circulation channel, the first circulation channel defining a first front section, a first curved section, and a first rear section, the first front section communicating with the first fracture, the first curved section communicating with the first front section and the first rear section respectively, the first rear section communicating with the second fracture, the second circulation channel defining a second front section, a second curved section, and a second rear section, the second front section communicating with the third fracture, the second curved section communicating with the second front section and the second rear section respectively, the second rear section communicating with the fourth fracture, the first and second curved sections being arranged along the threaded shaft and define a predetermined included angle therebetween with respect to the imaginary axis radially;
• and
• a plurality of rolling members running among the first and second threaded grooves and the first and second circulation channels.