Screw device

A rolling element screw device including:

• a screw shaft having a helical rolling element rolling groove in an outer peripheral surface thereof;
• a nut having a through-hole in which the screw shaft is rotatably placed, and a helical loaded rolling element rolling groove in an inner peripheral surface thereof, the helical loaded rolling element rolling groove facing the rolling element rolling groove;
• and a plurality of rolling elements placed between the rolling element rolling groove of the screw shaft and the loaded rolling element rolling groove of the nut in a manner capable of rolling motion, the nut having a communicating hole penetrating the nut in an axial direction, and a recess in an axial end surface, the recess communicating with the communicating hole and the loaded rolling element rolling groove, the recess of the nut accommodating a circulation member having a turn-around path linking to the loaded rolling element rolling groove and the communicating hole of the nut, the screw device comprising
• a clearance between the circulation member and a wall surface of the recess in such a manner as that the circulation member is movable, wherein
• the circulation member accommodated in the recess is covered with a lid member to be attached to the nuts the lid member being a separate body from the circulation member,
• the circulation member includes, at one end away from the communicating hole, a projection protruding from an opposing surface facing the lid member toward the lid member, and
• a clearance is provided between the opposing surface of the circulation member and the lid member.

A rolling element screw device including:

• a screw shaft having a helical rolling element rolling groove in an outer peripheral surface thereof;
• a nut having a through-hole in which the screw shaft is rotatably placed, and a helical loaded rolling element rolling groove in an inner peripheral surface thereof, the helical loaded rolling element rolling groove facing the rolling element rolling groove;
• and a plurality of rolling elements placed between the rolling element rolling groove of the screw shaft and the loaded rolling element rolling groove of the nut in a manner capable of rolling motion, the nut having a communicating hole penetrating the nut in an axial direction, and a recess in an axial end surface, the recess communicating with the communicating hole and the loaded rolling element rolling groove, the recess of the nut accommodating a circulation member having a turn-around path linking to the loaded rolling element rolling groove and the communicating hole of the nut, the screw device comprising
• a clearance between the circulation member and a wall surface of the recess in such a manner as that the circulation member is movable, wherein
• the circulation member accommodated in the recess is covered with a lid member to be attached to the nut, the lid member being a separate body from the circulation member,
• the circulation member includes
• at one end away from the communicating hole, a first projection protruding from an opposing surface facing the lid member toward the lid member, and
• at the other end close to the communicating hole, a second projection protruding from the opposing surface facing the lid member toward the lid member, and
• a clearance is provided between the opposing surface of the circulation member and the lid member.

A rolling element screw device including:

• a screw shaft having a helical rolling element rolling groove in an outer peripheral surface thereof;
• a nut having a through-hole in which the screw shaft is rotatably placed, and a helical loaded rolling element rolling groove in an inner peripheral surface thereof, the helical loaded rolling element rolling groove facing the rolling element rolling groove;
• and a plurality of rolling elements placed between the rolling element rolling groove of the screw shaft and the loaded rolling element rolling groove of the nut in a manner capable of rolling motion, the nut having a communicating hole penetrating the nut in an axial direction, and a recess in an axial end surface, the recess communicating with the communicating hole and the loaded rolling element rolling groove, the recess of the nut accommodating a circulation member having a turn-around path linking to the loaded rolling element rolling groove and the communicating hole of the nut, the screw device comprising
• a clearance between the circulation member and a wall surface of the recess in such a manner as that the circulation member is movable, wherein
• the circulation member accommodated in the recess is covered with a lid member to be attached to the nut, the lid member being a separate body from the circulation member,
• the recess includes a movement restriction recess adjacently to the communicating hole,
• the circulation member includes a movement restriction protrusion accommodated in the movement restriction recess, and
• when the nut is viewed from the axial direction, the movement restriction recess and the movement restriction protrusion come into contact with each other to restrict the movement of the circulation member in an X-axis direction in which the rolling element that has left the communicating hole moves toward the loaded rolling element rolling groove.