JPS5620848A - Hydraulic shock absorber for vehicle - Google Patents

Abstract

PURPOSE:To improve the ride comfort and steering a stability by a method wherein the damping force is varied in accordance with the piston stroke of a hydraulic shock absorber for vehicle, in such a manner as to satisfy both the characteristic for a low damping force range in a minute stroke range and the characteristic for the rated damping force range. CONSTITUTION:During the compression stroke, with the hydraulic pressure increased by the advance of a piston 4, the hydraulic pressure in an upper chamber 9 is increased through an orifice (not shown), the increased hydraulic pressure acts on a film coat 14 through an orifice 13, a gas chamber 16 is compressed, an amount of the oil corresponding to the compressive deformation escapes into the clearance between the film coat 14 and the inner cylinder wall 2a, to obtain a low initial-stage damping force and provide an antivibration effect against the small ruggedness of the road surface. When the stroke further grows larger, the hydraulic pressure in the chamber 9 becomes equal to the sum of the maximum pressure in the gas chamber 16 and the elastic force of the film coat, a bottom valve 11 operates, and the hydraulic oil flows out into a chamber 8 to generate the rated damping force. During the extended stroke, the hydraulic oil is inclined to flow out of the chamber 9, whereby the hydraulic pressure is increased and the valve of the piston 4 is opened, and the oil flows out into a lower chamber 10 through the orifice.