US 12,109,608 B2
Method of manufacturing steering shaft
Takateru Seki, Hitachinaka (JP); Norihiro Kimura, Hitachinaka (JP); and Takeo Okabe, Hitachinaka (JP)
Assigned to HITACHI ASTEMO, LTD., Hitachinaka (JP)
Appl. No. 17/637,759
Filed by HITACHI ASTEMO, LTD., Hitachinaka (JP)
PCT Filed Jun. 5, 2020, PCT No. PCT/JP2020/022237
§ 371(c)(1), (2) Date Feb. 23, 2022,
PCT Pub. No. WO2021/044685, PCT Pub. Date Mar. 11, 2021.
Claims priority of application No. 2019-160315 (JP), filed on Sep. 3, 2019.
Prior Publication US 2022/0280995 A1, Sep. 8, 2022
Int. Cl. B21H 3/04 (2006.01); B21K 1/76 (2006.01); B23K 20/12 (2006.01); B62D 3/12 (2006.01); B62D 5/04 (2006.01)
CPC B21H 3/04 (2013.01) [B23K 20/12 (2013.01); B62D 3/12 (2013.01); B62D 5/0448 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A method of manufacturing a steering shaft of a steering device, the steering shaft having a bar shape, and including a first end portion, a second end portion, and an intermediate portion formed between the first end portion and the second end portion,
the method comprising:
a rolling die abutment step of bringing a rolling die into abutment against a workpiece being a material for forming the steering shaft; and
a ball screw groove forming step of forming a ball screw groove in the workpiece in a first state,
wherein in the rolling die abutment step, the rolling die is brought into abutment against the intermediate portion of the workpiece in the first state, and
wherein in the ball screw groove forming step, the workpiece is moved relative to the rolling die so that a region of the workpiece against which the rolling die is brought into abutment is moved from the intermediate portion toward the first end portion, thereby forming the ball screw groove in the workpiece and forming the workpiece in a second state,
the method of manufacturing the steering shaft further comprising a diameter-reduced portion forming step and a friction welding step,
wherein the steering shaft includes:
a first member, which has the ball screw groove formed therein, and includes the first end portion and the intermediate portion; and
a second member, which is connected to the first member, and includes the second end portion, and
wherein when an axis of the first member, which passes a center of the steering shaft in a cross section orthogonal to a longitudinal direction of the steering shaft and is parallel to the longitudinal direction of the steering shaft, is defined as a center axis,
in the diameter-reduced portion forming step, under a state in which the ball screw groove is formed in the first member in the ball screw groove forming step, a predetermined range of the first member including the intermediate portion is cut by machining so that a radially outer diameter of the first member with respect to the center axis of the first member is equal to an outer diameter of a bottom of the ball screw groove, and
in the friction welding step, an end portion of the first member opposite to the first end portion, and an end portion of the second member opposite to the second end portion are joined to each other by friction welding.