Hydraulic valve-operating system for internal combustion engines

Abstract

A fluidic valve-operating system has a reciprocally-movable plunger for moving a valve of an internal combustion engine between closed and opened conditions. A main circuit has feed and return paths for flow of hydraulic fluid from a reservoir to the plunger and a pump interposed in the feed path and driven by the engine. A breather circuit has feed and return paths for flow of hydraulic fluid from an accumulator to the plunger. A control valve interposed in the feed and return paths of the respective main and breather circuits is actuatable by a piezoelectric valve for switching each of the main and breather circuits between pressure supply and return flow modes with respect to the plunger. The main circuit when switched to its pressure supply mode applies a drive pressure to the plunger which varies proportionally with the speed of the engine to accelerate the plunger along a drive stroke to move the valve form its closed toward its opened condition. The breather circuit allows pressure relief when the plunger has moved a portion of its total stroke. A chamber containing a gas is connected in flow communication with the pump via a piston to provide a variable pressure spring for applying a return pressure to the plunger which varies proportionally with engine speed, opposes but is less than the drive pressure and causes deceleration and return of the plunger to its initial position when main and breather circuits are in return flow modes.