Patent ID: 6782980
Filing Date: 2004-08-31
Classification: F16F

Abstract:
A controllable damping force hydraulic shock absorber comprising:a cylinder in which a hydraulic fluid is sealably contained; a piston slidably fitted in the cylinder; a piston rod having one end connected to the piston and the other end extended to the outside of the cylinder; an extension-stroke passage which allows flow of the hydraulic fluid during an extension stroke of the piston rod; a compression-stroke passage which allows flow of the hydraulic fluid during a compression stroke of the piston rod; an extension-stroke pilot type damping force control valve in which the flow of the hydraulic fluid in the extension-stroke passage is controlled due to the effect of a pressure in a pilot chamber, to thereby generate a damping force; and a compression-stroke pilot type damping force control valve in which the flow of the hydraulic fluid in the compression-stroke passage is controlled due to the effect of a pressure in a pilot chamber, to thereby generate a damping force, each of the extension-stroke pilot type damping force control valve and the compression-stroke pilot type damping force control valve including a pilot control valve provided therein so as to control the hydraulic fluid in the pilot chamber, wherein one of the pilot control valve provided in the extension-stroke pilot type damping force control valve and the pilot control valve provided in the compression-stroke pilot type damping force control valve comprises a flow rate control valve, the flow rate control valve being adapted to control a flow path area of a flow passage connected to the pilot chamber of the one pilot control valve to a desired flow path area by means of an actuator, and the other pilot control valve comprises a pressure control valve, the pressure control valve being adapted to control the pressure in the pilot chamber of the other pilot control valve to a desired pressure by means of an actuator.