US 11,054,007 B2
Lead screw structure and assembly and rear wheel steering apparatus using the same
Kyung Sub Shin, Seoul (KR); and Han Sang Chae, Seongnam-si (KR)
Assigned to MANDO CORPORATION, Pyeongtaek-si (KR)
Filed by MANDO CORPORATION, Pyeongtaek-si (KR)
Filed on Dec. 14, 2017, as Appl. No. 15/842,732.
Claims priority of application No. 10-2016-0181951 (KR), filed on Dec. 29, 2016.
Prior Publication US 2018/0187758 A1, Jul. 5, 2018
Int. Cl. F16H 25/20 (2006.01); B62D 3/06 (2006.01); B62D 5/04 (2006.01); B62D 7/15 (2006.01)
CPC F16H 25/2006 (2013.01) [B62D 3/06 (2013.01); B62D 5/0403 (2013.01); B62D 5/0421 (2013.01); B62D 5/0424 (2013.01); B62D 5/0445 (2013.01); B62D 7/1581 (2013.01); F16H 25/2015 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A lead screw structure comprising:
a screw shaft having a thread on an outer circumferential surface thereof;
a nut unit coupled to the screw shaft such that a thread formed on an inner circumferential surface of the nut unit is directly engaged with the thread of the screw shaft, the nut unit including a first nut member and a second nut member; and
a first elastic member disposed between the first nut member and the second nut member to provide an elastic force to the nut unit in an axial direction of the screw shaft, thereby compensating for a gap between the thread of the outer circumferential surface of the screw shaft and the thread of the inner circumferential surface of the nut unit that is directly engaged with the thread of the screw shaft,
wherein the first elastic member is a wave washer having a ring shape with bent sides,
the second nut member includes a portion extending into an opening of the first nut member,
the first nut member has a first inner circumferential surface to which the screw shaft is coupled and a second inner circumferential surface having a first serration formed in a longitudinal direction of the screw shaft, a diameter of the second inner circumferential surface being greater than a diameter of the first inner circumferential surface,
the second nut member has a second serration disposed on an outer circumferential surface of the portion extending into the opening of the first nut member, in the longitudinal direction of the screw shaft, the second serration corresponding to the first serration, the first nut member and the second nut member being coupled to each other using the first and second serrations,
the first elastic member is disposed between the first nut member and an end surface of the portion, on which the second serration is disposed, of the second nut member, and
the end surface of the portion, on which the second serration is disposed, of the second nut member, is an innermost portion of the entire second nut member, with respect to the opening of the first nut number in the axial direction of the screw shaft.