Control device for hydraulically operated tappet valves of internal combustion engines

Claim 1

In a control device for hydraulically operated tappet valves of an internal combustion engine, said device being of the type that includes a reciprocating actuating piston mechanically connected to an associated tappet valve for periodically opening the latter against the force of a valve closing resilient means, the improvement comprising A. a source continuously supplying pressurized hydraulic liquid, B. first channel means connecting said source with said actuating piston for delivering pressurized hydraulic liquid to said actuating piston for exerting an opening force thereon, C. a hydraulic servo means having 1. a hydraulically operated valve situated in said first channel means and adapted to assume a first position in which it blocks delivery of said pressurized hydraulic liquid to said actuating piston and a second position for maintaining direct hydraulic communication between said source and said actuating piston for allowing delivery of said pressurized hydraulic liquid to said actuating piston, 2. means for urging said hydraulically operated valve into said first position, 3. second channel means connecting said source with said hydraulically operated valve for delivering pressurized hydraulic liquid to said hydraulically operated valve for exerting a force thereon to move it into said second position, said first channel means and said second channel means being connected in parallel between said source and said hydraulically operated valve, 4. a solenoid valve situated in said second channel means and adapted to assume a first position in which it blocks delivery of said last-named pressurized hydraulic liquid to said hydraulically operated valve and a second position in which it allows delivery of said last-named pressurized hydraulic liquid to said hydraulically operated valve, said first channel means fully circumventing said solenoid valve, 5. means for urging said solenoid valve into its first position and D. means for intermittently energizing said solenoid valve for moving it periodically into its second position.