Patent ID: 7878311

Claim:
A piston for a vibration damper that has a cylinder and a piston assembly with a rod extending out of the cylinder, the piston assembly includes a piston slidably received within the cylinder thereby defining a compression chamber and a rebound chamber each having fluid under pressure therein, the piston comprising: a piston body that has a bore with a valve seat therein through which fluid flows between the compression and rebound chambers; a poppet engaging and disengaging the valve seat; a pilot chamber on a side of the poppet remote from the valve seat; a first logic arrangement which applies a greater one of the pressure in the compression and the pressure in the rebound chamber to the pilot chamber; a pressure cavity in the piston body; a pilot valve member varying an amount of fluid flow between the pilot chamber and the pressure cavity; a second logic arrangement which opens the pressure cavity to whichever of the compression and rebound chambers has a lower pressure than pressure in the pressure cavity; a first fluid passage opening into the pilot chamber; a vent orifice opening into the pilot chamber and providing a smaller flow path than the first fluid passage; and a second fluid passage opening into the pressure cavity, wherein the pilot valve member comprises a pilot spool selectively providing fluid communication between the first fluid passage, the vent orifice and the second fluid passage; and an electrically operated actuator that moves the pilot valve member.