Patent ID: 6293377
Filing Date: 2001-09-25
Classification: F16F

Abstract:
A variable-damping force shock absorber comprising:a cylinder containing an operating fluid; a piston slidably mounted in the cylinder slidably for motion in a direction of an axis of the cylinder, the piston dividing the cylinder into a first chamber and a second chamber;a hollow piston rod, a first end portion of the piston rod being connected to the piston and a second end portion of the piston rod protruding from an end face of the cylinder;a communication passage connecting the first and second chambers of the cylinder;a valve mechanism provided at the first end portion of the piston rod, the valve mechanism having a spool movable in a direction of a piston rod axis, the valve mechanism changing an opening of the communication passage in accordance with a displacement of the spool in the direction of the piston rod axis;an actuator including a stator mounted to an inner peripheral face of the piston rod, a rotor facing the stator so as to rotate about the piston rod axis relative to the stator, and a rotating body supported for rotation about the piston rod axis at the inner peripheral surface of the piston rod, the rotating body and the rotor being fixed to each other so that the rotating body rotates together with the rotor, wherein the actuator outputs a rotating drive force created by rotation of the rotor, via the rotating body; anda drive force converting mechanism that converts the rotating drive force from the actuator into a drive force in the direction of the piston rod axis and transfers the drive force to the spool of the valve mechanism to displace the spool in the direction of the piston rod axis,wherein the rotor of the actuator and the drive force converting mechanism are separated in the direction of the piston rod axis,wherein the drive force converting mechanism includes a shaft disposed in the piston rod so that the shaft is allowed to move in the direction of the piston rod axis and is prevented from turning about the piston rod axis, a first end portion of the shaft being connected to the spool and a screw mechanism having a first screw portion being formed in a second end portion of the shaft, wherein a second screw portion is formed in the rotating body of the actuator, the first and second screw portions being engaged with one another, the screw mechanism displacing the shaft in the direction of the piston rod axis as the rotating body rotates,wherein the rotating body of the actuator is cylindrical and coaxial with the piston rod axis,wherein the rotor is embedded in a side face of the rotating body and an insert hole into which the first end portion of the shaft is inserted is formed in an end face of the rotating body, andwherein the screw mechanism includes a female thread formed in the insert hole of the rotating body and a male thread formed on an outer peripheral face of the first end portion of the shaft.