US 12,072,004 B1
Linear actuator
Motoshi Sakai, Tokyo (JP)
Assigned to NSK LTD., Tokyo (JP)
Appl. No. 18/292,008
Filed by NSK LTD., Tokyo (JP)
PCT Filed Apr. 4, 2023, PCT No. PCT/JP2023/013952
§ 371(c)(1), (2) Date Jan. 25, 2024,
PCT Pub. No. WO2023/204016, PCT Pub. Date Oct. 26, 2023.
Claims priority of application No. 2022-071135 (JP), filed on Apr. 22, 2022.
Int. Cl. F16H 25/22 (2006.01); F16H 25/20 (2006.01)
CPC F16H 25/2214 (2013.01) [F16H 25/2015 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A linear actuator comprising:
a ball screw device including a nut, a screw shaft, and a plurality of balls;
a piston attached to one end portion of the screw shaft; and
a rotation stopper that sets an initial position of the screw shaft in a first direction indicated by the one end portion, wherein
the screw shaft includes
a screw shaft body provided with an outer peripheral raceway surface,
a male spline portion that protrudes in the first direction from an end portion in the first direction of the screw shaft body and that has a smaller diameter than the screw shaft body, and
a step surface that is provided at a boundary between the screw shaft body and the male spline portion and that faces the first direction,
the nut includes
an annular first end surface facing the first direction,
a first opening portion which is located in an inner periphery of the first end surface and into which the screw shaft is inserted, and
a first stopper protruding from the first end surface in the first direction,
the piston includes
a piston body having a pressing surface facing the first direction and an opposite surface facing a second direction opposite to the first direction,
a cylindrical portion that has a cylindrical shape, protrudes from a central portion of the opposite surface in the second direction, and is fitted into the male spline portion, and
a second stopper that protrudes from the opposite surface in the second direction and is continuous with an outer peripheral surface of the cylindrical portion,
the first stopper and the second stopper abut on each other and form the rotation stopper in a case where the screw shaft is at the initial position,
the step surface is arranged in the second direction compared to the first opening portion and is located inside the nut in a case where the screw shaft is at the initial position,
the cylindrical portion protrudes in the second direction compared to the second stopper and abuts on the step surface, and
an outer peripheral surface of the cylindrical portion has a larger diameter than a groove bottom of the outer peripheral raceway surface.