Patent ID: 7946399
Filing Date: 2011-05-24
Classification: F16F

Abstract:
1. A hydraulic shock absorber having: a cylinder filled with hydraulic oil; a piston disposed slidably within the cylinder, for dividing an inside of the cylinder into a first oil chamber and a second oil chamber; and a main valve composed of a spool and a disc on which the spool is seated, the main valve being provided on the piston and disposed in a main passage through which the first oil chamber and the second oil chamber communicate with each other, the absorber comprising: an extension-side pilot chamber formed in a back face of the spool, for urging the spool in a valve-closing direction through a pilot pressure introduced via a first orifice from the either oil chamber which is at high pressure in an extension stroke; a compression-side pilot chamber formed in the back face of the spool, for urging the spool in the valve-closing direction through a pilot pressure introduced via a second orifice from the either oil chamber which is at high pressure in a compression stroke; an extension-side pressure-receiving portion provided on the spool and having a smaller pressure-receiving area than the extension-side pilot chamber, for allowing pressure to be introduced into the extension-side pressure-receiving portion from an oil chamber which is at high pressure in the extension stroke and urging the spool in a valve-opening direction against the extension-side pilot pressure; a compression-side pressure-receiving portion provided on the spool and having a smaller pressure-receiving area than the compression-side pilot chamber, for allowing pressure to be introduced into the compression-side pressure-receiving portion from an oil chamber which is at high pressure in the compression stroke and urging the spool in the valve-opening direction against the compression-side pilot pressure; an extension-side poppet valve which opens when pressure in the extension-side pilot chamber reaches cracking pressure for holding the pilot pressure substantially below the cracking pressure; a compression-side poppet valve which opens when pressure in the compression-side pilot chamber reaches cracking pressure for holding the pilot pressure substantially below the cracking pressure; and a solenoid for allowing a current to flow therethrough to be excited and applying an urging force in such a direction that the solenoid reduces initial loads of springs of the extension-side poppet valve and the compression-side poppet valve; wherein the extension-side poppet valve and the compression-side poppet valve have a single common pilot passage for introducing a pilot pressure to each of the valves; the pilot passage has a first check valve and a second check valve disposed in the pilot passage: the first check valve and the second check valve are located upstream of the extension-side poppet valve and downstream of the compression-side poppet valve, respectively, open due to flow of hydraulic oil in opposite directions, and have the first orifice and the second orifice, respectively; the compression-side poppet valve is seated on a seat hole portion of the spool; the extension-side poppet valve is seated on a seat hole portion of the compression-side poppet valve; the extension-side poppet valve and the compression-side poppet valve are equipped with a single spring for urging the extension-side poppet valve and the compression-side poppet valve in a valve-closing direction; the extension-side poppet valve releases the extension-side pilot pressure via the seat hole portion of the compression-side poppet valve in moving away from the compression-side poppet valve and opening against the spring by the extension-side pilot pressure; and the compression-side poppet valve moves away from the seat hole portion of the spool integrally with the extension-side poppet valve to release the compression-side pilot pressure in opening against the spring by the compression-side pilot pressure.