Manufacturing method of ball screw using rolling machine

Patent metadata

Field	Value
Publication number	US-12454000-B2
Application number	US-202118272231-A
Country	US
Kind code	B2
Filing date	Dec 10, 2021
Priority date	Jan 19, 2021
Publication date	Oct 28, 2025
Grant date	Oct 28, 2025

Abstract

A rolling machine has a rolling die 4 that forms a male screw by pressing a steering shaft 14 which is an object to be rolled and plastically deforming an outer peripheral surface of the steering shaft 14 while rotating in contact with the outer peripheral surface of the steering shaft 14, a main spindle 3 inserted into a penetration hole 10 of the rolling die 4 and transmitting a rotation force to the rolling die 4, a key groove and a key which restrict a relative rotation between the rolling die 4 and the main spindle 3, a spiral oil groove 16 provided on an inner peripheral surface of the penetration hole 10 or an outer peripheral surface of the main spindle and extending from one end portion 10b side in an axial direction of the penetration hole in an inner axial direction of the penetration hole.

First claim

The invention claimed is:

1. A method for manufacturing a ball screw using a rolling machine, the rolling machine including:
a rolling die structured to form a male screw by pressing a shaft-shaped member and plastically deforming an outer peripheral surface of the shaft-shaped member while rotating in contact with the outer peripheral surface of the shaft-shaped member;
a main spindle inserted into a penetration hole of the rolling die, which is formed so as to penetrate the rolling die in a direction of a rotation axis of the rolling die, and transmitting a rotation force to the rolling die;
a restricting portion restricting a relative rotation of the rolling die with respect to the main spindle; and
a linear oil groove provided on an inner peripheral surface of the penetration hole or an outer peripheral surface of the main spindle and extending from an end portion side in an axial direction of the penetration hole in an inner axial direction of the penetration hole,
wherein the ball screw has a nut which has a female thread formed on an inner peripheral surface of the nut, the metal shaft-shaped member to which the nut is assembled and which has the male screw formed on the outer peripheral surface of the shaft-shaped member and facing the female thread, and a plurality of balls disposed between the female thread and the male screw,
the method comprising:
forming the male screw by bringing the rolling die, which is rotating by the rotation force transmitted from the main spindle, into contact with the outer peripheral surface of the shaft-shaped member, pressing the shaft-shaped member and plastically deforming the outer peripheral surface of the shaft-shaped member; and
when replacing the rolling die which is a pre-replacement rolling die, using a rolling die which is a post-replacement rolling die having the oil groove whose forming position in a circumferential direction is different from that of the pre-replacement rolling die.

2. The method for manufacturing the ball screw using the rolling machine as claimed in claim 1 , wherein
a plurality of rolling dies for the replacement each have a marking portion formed at a same position in the circumferential direction, and
the oil grooves of the plurality of rolling dies are different from each other in a forming position of the oil groove with respect to the marking portion in the circumferential direction.

3. The method for manufacturing the ball screw using the rolling machine as claimed in claim 2 , wherein
the marking portion is a key groove formed from a hole edge of the penetration hole in the inner axial direction of the penetration hole, and
by inserting a key into the key groove from the axial direction and fixing the key to the key groove, the relative rotation of the rolling die with respect to the main spindle is restricted.

4. The method for manufacturing the ball screw using the rolling machine as claimed in claim 1 , wherein
the ball screw is used in an electric power steering device that gives a steering force by moving the shaft-shaped member in the axial direction by transmitting a rotation force of an electric motor to the nut.

Assignees

• Hitachi Astemo Ltd

Inventors

• Hashimoto Kinichi
• Kitamura Keisuke

Classifications

• B21K1/04

  ball-races {or sliding bearing races} · CPC title

• B21K1/56 Primary

  screw-threaded elements · CPC title

• B21H3/04 Primary

  Making by means of profiled-rolls {or die rolls} · CPC title