Patent ID: 6182805
Filing Date: 2001-02-06
Classification: F16F

Abstract:
A damping force control type hydraulic shock absorber comprising:a cylinder having a hydraulic fluid sealed therein;a piston slidably fitted in said cylinder;a piston rod connected at one end thereof to said piston, the other end of said piston rod extending to an outside of said cylinder;a main hydraulic fluid passage and a sub-hydraulic fluid passage which are connected to said cylinder to pass the hydraulic fluid in response to sliding movement of said piston;a pilot-type damping valve provided in said main hydraulic fluid passage; anda fixed orifice and a pressure control valve which are provided in said sub-hydraulic fluid passage;wherein a pressure between said fixed orifice and said pressure control valve in said sub-hydraulic fluid passage is used as a pilot pressure of said pilot-type damping valve, andwherein said pressure control valve is a solenoid-controlled valve in which a valving element constantly urged in a valve opening direction by an urging device is urged in a valve closing direction by thrust from a solenoid to control a flow path area of said sub-hydraulic fluid passage by a balance between urging force from said urging device and the thrust from said solenoid, thereby adjusting said pilot pressure, andwherein a fail-safe valve is provided in said sub-hydraulic fluid passage, said fail-safe valve being arranged such that it is opened by thrust from said solenoid, and when the thrust from said solenoid is less than a predetermined level, said fail-safe valve restricts said sub-hydraulic fluid passage by the urging force from said urging device.