Method for Manufacturing Ball Screw and Ball Screw

Abstract

A method for manufacturing a ball screw according to the present invention includes a seal fixing step of fixing a ring shaped seal ( 4 ) to an attachment portion ( 24 ) disposed in an end portion of a nut ( 2 ) of a ball screw in an axis direction using a fixing member ( 5 ). The attachment portion has an inner circumferential surface having a diameter larger than that of an inner circumferential surface on which a spiral groove of the nut is formed. A through hole ( 25 a to 25 c ) is formed in the attachment portion, the through hole ( 25 a to 25 c ) penetrating the attachment portion in a radial direction from an outer circumferential surface thereof to the inner circumferential surface thereof. The seal fixing step includes passing the screw through the through hole and engaging the screw with an outer circumferential portion of the ring shaped seal to exert an outward-directed force in the radial direction on the ring shaped seal because of a force of the head pressing the bearing face to fix the ring shaped seal to the nut.

1 . A method for manufacturing a ball screw, the method comprising:
 a seal fixing step of fixing a ring shaped seal to an attachment portion disposed in an end portion of a nut of the ball screw in an axis direction using a fixing member,   wherein the attachment portion has an inner circumferential surface having a diameter larger than a diameter of an inner circumferential surface on which a spiral groove of the nut is formed,   a through hole is formed in the attachment portion, the through hole penetrating the attachment portion in a radial direction from an outer circumferential surface of the attachment portion to the inner circumferential surface of the attachment portion, and   the seal fixing step includes passing the fixing member through the through hole and engaging the fixing member with an outer circumferential portion of the ring shaped seal to exert an outward-directed force in the radial direction on the ring shaped seal and to fix the ring shaped seal to the nut.   
     
     
         2 . A method for manufacturing a ball screw, the method comprising:
 a seal fixing step of fixing a ring shaped seal to an attachment portion disposed in an end portion of a nut of the ball screw in an axis direction using a fixing member,   wherein the attachment portion has an inner circumferential surface having a diameter larger than a diameter of an inner circumferential surface on which a spiral groove of the nut is formed,   a screw having a head is used as the fixing member,   a through hole is formed in the attachment portion, the through hole penetrating the attachment portion in a radial direction from an outer circumferential surface of the attachment portion to the inner circumferential surface of the attachment portion and having a bearing face for bearing the head of the screw, and   the seal fixing step includes passing the screw through the through hole and engaging the screw with an outer circumferential portion of the ring shaped seal to exert an outward-directed force in the radial direction on the ring shaped seal because of a force of the head pressing the bearing face to fix the ring shaped seal to the nut.   
     
     
         3 . The method for manufacturing the ball screw according to  claim 2 , wherein
 an attachment hole is formed in the ring shaped seal, the attachment hole extending in the radial direction from the outer circumferential surface of the ring shaped seal, and   the seal fixing step includes matching positions of the attachment hole and the through hole with each other, and passing the screw through the through hole to engage the screw with the attachment hole.   
     
     
         4 . The method for manufacturing the ball screw according to  claim 3 , wherein
 the attachment hole is a concave portion extending in the radial direction from the outer circumferential surface of the ring shaped seal,   the through hole includes a large-diameter portion on an outer circumference side, a small-diameter portion on an inner circumference side, and a conical portion communicating between the large-diameter portion and the small-diameter portion,   a diameter of the large-diameter portion is larger than a diameter of the head of the screw,   a diameter of the small-diameter portion is larger than an outer diameter of a male screw portion of the screw,   an inclined surface of the conical portion serves as the bearing face for bearing the head,   the ring shaped seal is disposed in the attachment portion,   the method including:
 using a drill having a bit portion at a tip of a shank portion of the drill and an inclined surface formed in a boundary portion between the shank portion and the bit portion, the inclined surface corresponding the inclined surface of the through hole, a diameter of the bit portion being smaller than a diameter of the shank portion, the diameter of the shank portion being larger than the diameter of the small-diameter portion of the through hole and smaller than the diameter of the large-diameter portion; and 
 forming the concave portion in the ring shaped seal by inserting the drill into the through hole until a position where the inclined surface of the shank portion comes in contact with the inclined surface of the through hole. 
   
     
     
         5 . A ball screw comprising:
 a nut having an inner circumferential surface on which a spiral groove is formed;   a threaded shaft having an outer circumferential surface on which a spiral groove is formed;   balls allocated in a raceway formed by the spiral groove of the nut and the spiral groove of the threaded shaft;   a ring shaped seal fixed to an attachment portion disposed in an end portion of the nut in an axis direction; and   a screw having a head, wherein   the attachment portion has an inner circumferential surface having a diameter larger than a diameter of the inner circumferential surface on which the spiral groove of the nut is formed,   a through hole is formed in the attachment portion, the through hole penetrating the attachment portion in a radial direction from an outer circumferential surface of the attachment portion to the inner circumferential surface of the attachment portion,   the through hole has a bearing face for bearing the head of the screw, and   the screw passes through the through hole and engages with an outer circumferential portion of the ring shaped seal to exert an outward-directed force in the radial direction on the ring shaped seal because of a force of the head pressing the bearing face to fix the ring shaped seal to the nut.   
     
     
         6 . The ball screw according to  claim 5 , wherein
 the screw is a tapping screw,   the ring shaped seal has an attachment hole at a position corresponding to the through hole, the attachment hole extending in the radial direction from an outer circumferential surface of the ring shaped seal,   the attachment hole is a pilot hole of which a hole diameter is equal to or less than a root diameter of a male screw portion of the tapping screw and in which a female screw is not formed, and   the male screw portion of the tapping screw passing through the through hole is coupled to a portion of the pilot hole of the ring shaped seal in a state the male screw portion cuts a thread.   
     
     
         7 . The ball screw according to  claim 5 , wherein
 the screw is a self-drill screw, and   a male screw portion of the self-drill screw passing through the through hole is coupled to the outer circumferential portion of the ring shaped seal in a state the male screw portion cuts a thread.