US 11,867,262 B2
Frictional roller reducer
Hiroshi Kawahara, Fujisawa (JP); and Hirofumi Itagaki, Fujisawa (JP)
Assigned to NSK, LTD., Tokyo (JP)
Appl. No. 17/440,950
Filed by NSK LTD., Tokyo (JP)
PCT Filed Jan. 10, 2020, PCT No. PCT/JP2020/000683
§ 371(c)(1), (2) Date Sep. 20, 2021,
PCT Pub. No. WO2020/188967, PCT Pub. Date Sep. 24, 2020.
Claims priority of application No. 2019-053690 (JP), filed on Mar. 20, 2019.
Prior Publication US 2022/0221031 A1, Jul. 14, 2022
Int. Cl. F16H 13/08 (2006.01); F16H 13/10 (2006.01)
CPC F16H 13/10 (2013.01) [F16H 13/08 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A frictional roller reducer, comprising:
an input shaft;
an inner-diameter side rolling contact surface configured by an outer circumferential surface of the input shaft, or by an outer circumferential surface of a portion that integrally rotates with the input shaft;
an output shaft that is coaxial with the input shaft and supported so as to be able to rotate relative to the input shaft;
a pair of annular roller elements that are prevented from rotating around the input shaft and are arranged with a gap between tip-end surfaces thereof facing each other; where an inner circumferential surface of each of the pair of annular roller elements is configured by an outer-diameter side rolling contact surface that faces the inner-diameter side rolling contact surface, and is inclined in a direction in which an inner diameter dimension increases as going toward a tip-end surface side thereof, and at least one annular roller element of the pair of annular roller elements is supported so as to be able to displace in an axial direction, and has a driven-side cam surface on a base end surface facing toward an opposite side in the axial direction from the tip-end surface thereof;
a plurality of planetary rollers, each having a rotation shaft arranged parallel to the input shaft, and a rolling surface that comes in rolling contact with the inner-diameter side rolling contact surface and the outer-diameter side rolling contact surfaces;
a carrier that supports the plurality of planetary rollers so at to be able to rotate freely around the rotation shaft and to be able to displace in a radial direction, and integrally configured with the output shaft or configured by a member that integrally rotates with the output shaft;
a pressing device that includes:
a cam disk that is supported around the input shaft so as to be able to rotate relative to the input shaft and so as not to be able to displace in the axial direction, having a drive side cam surface on a side surface in the axial direction that faces the driven side cam surface;
a plurality of rolling bodies held between the driven side cam surface and the drive side cam surface; and
a pressing force adjusting motor that rotationally drives the cam disk; and
based on rotational driving in a specified direction of the cam disk by the pressing force adjusting motor, is able to press the pair of annular roller elements in directions toward each other; and
a controller that, by adjusting a rotational drive of the pressing force adjusting motor, is able to adjust surface pressure at traction portions between the rolling surfaces and the inner-diameter side rolling contact surface and the outer-diameter side rolling contact surfaces to a target value;
wherein the controller, by adjusting the rotational drive of the pressing force adjusting motor so as to rotationally drive the cam disk in a direction opposite to the specified direction during coasting, displacing the planetary rollers outward in the radial direction due to centrifugal force while the pair of annual roller elements is caused to displace in a direction away from each other, is able to make a surface pressure at the rolling contact portions between the rolling surfaces and the inner-diameter side rolling contact surface substantially zero.