Thrust transfer device
A thrust transfer device includes: a motor serving as a driving source; a sun gear rotatable to an output shaft of the motor, a plurality of nut members each provided with an outer peripheral external tooth meshed with the sun gear and provided with an inner peripheral nut side spiral screw groove; and a plurality of screw shafts, each provided, at an outer periphery thereof, with a screw side spiral screw groove corresponding to the nut side spiral screw groove, and reciprocally moved in accordance with nut rotation by fitting the screw side screw groove into the nut side screw groove; and an internal tooth gear meshed with the external tooth formed to each of the nut members. When the sun gear is rotated, the nut members perform planetary motion inside the internal tooth gear, by which the screw shafts are reciprocally moved in axial directions thereof.
1. A thrust transfer device comprising:
a motor serving as a driving source;
a sun gear mounted to be rotatable to an output shaft of the motor,
a plurality of nut members each provided, at an outer periphery thereof, with an external tooth meshed with the sun gear and provided with, on an inner peripheral surface thereof, with a nut side spiral screw groove;
a plurality of screw shafts, each provided, at an outer periphery thereof, with a screw side spiral screw groove corresponding to the nut side spiral screw groove, and reciprocally moved in accordance with rotating motion of the nut member by fitting the screw side screw groove into the nut side screw groove; and
an auxiliary plate fixed to one of side end portions of the plural screw shafts and a pressing plate fixed to another of the side end portions of the plural screw shafts,
wherein thrust generated by the reciprocating motion of the screw shafts is transferred through the pressing plate, and
wherein when the sun gear is rotated, the nut members are rotated, and according to the rotating motion of the nut members, the screw shafts are reciprocally moved in axial directions thereof.
2. The thrust transfer device according to claim 1 , wherein the nut side screw grooves formed to the nut members and the screw side screw grooves formed to the screw shafts are fitted together through rolling members.
3. The thrust transfer device according to claim 1 ,
further comprising an internal tooth gear meshed with the external tooth formed to each of the nut members,
wherein when the sun gear is rotated, the nut members perform planetary motion inside the internal tooth gear, and according to the planetary motion thereof, the screw shafts are reciprocally moved in axial directions thereof.
4. The thrust transfer device according to claim 3 , further comprising:
a thrust bearing disposed on a surface opposite to the screw shaft connection surface of the pressing plate,
wherein one of track races of the thrust bearing is fixedly mounted to the pressing plate and another one of the track races is mounted in a non-restricted manner, the one of the track races absorbs a rotating motion generated by the planetary motion of the nut members and another one of the track races transfers only thrust generated by the reciprocating motion of the screw shafts.
5. The thrust transfer device according to claim 3 , further comprising:
a motor for control, and a gear for control mounted to be rotatable to a motor shaft of the motor for control,
wherein the internal tooth gear is provided, on an outer periphery thereof, with an external tooth for control and the control external tooth is connected to the control gear through a geared belt, so that the thrust generated by the reciprocating motion of the plural screw shafts becomes controllable.