Hydraulic shock absorber

Claim 1

In a hydraulic shock absorber including a cylinder containing a hydraulic fluid, a piston slidably received in said cylinder and defining first and second fluid chambers in said cylinder, said piston having first and second opposite end faces respectively facing said first and second chambers, a piston rod secured at one end thereof to said piston and having another end extending outside said cylinder, and a damping force generating mechanism attached to said piston, the improvement wherein said damping force generating mechanism comprises: a first passage formed in said piston and communicated with said first chamber and with a recess in said second end face of said piston; a second passage formed in said piston and communicated with said second chamber and with a recess in said first end face of said piston; a first disc valve assembly mounted on said second end face of said piston and having an inner peripheral portion secured to said piston and an outer peripheral portion deflectable to open and close said first passage; a second disc valve assembly mounted on said first end face of said piston and having an inner peripheral portion secured to said piston and an outer peripheral portion deflectable to open and close said second passage; and each of said first and second disc valve assemblies comprising: a first disc valve mounted on the respective said end face of said piston and having an opening communicated with said recess in said respective end face; a second disc valve mounted on said first disc valve, said second disc valve having formed therein a fluid passage having a first end open to the respective said chamber at that side of said piston at which said each disc valve assembly is disposed and a second end open to an interfacial area between said first and second disc valves; and said first disc valve, upon said piston being moved in said cylinder in a direction into said respective chamber at speeds in a relatively low speed range, being deformable away from said second disc valve by a resultant pressure that is generated in said respective chamber and that is insufficient to deform said outer peripheral portion of the other said disc valve assembly disposed at the other said end face of said piston, such that hydraulic fluid is allowed to flow from said respective chamber and said fluid passage in said second disc valve, through a clearance defined between said first and second disc valves due to such deformation, and then into the other said chamber, thereby generating damping force with valve characteristics in said low speed range.