Duration extender variable valve actuation

Abstract

A hydro-mechanical variable valve actuation (or VVA) system that controllably extends the valve duration. The valve opens up to its maximum lift mechanically/conventionally. The hydraulic part of the system controllably retards the closing of the valve, and takes part only during the valve-closing phase.

1 . A variable valve actuation system comprising at least:
 a camshaft ( 1 );   a cam ( 2 ) mounted on said camshaft ( 1 ), said cam ( 2 ) having an opening contour ( 3 ) and a closing contour ( 4 );   a valve ( 5 );   a cam-follower valve-actuator assembly ( 6 ), said cam ( 2 ), said valve ( 5 ) and said cam-follower valve-actuator assembly ( 6 ) translate the opening contour ( 3 ) into a theoretical opening valve lift pattern ( 7 ) and the closing contour ( 4 ) into a theoretical closing valve lift pattern ( 8 );   a valve spring ( 9 ) for restoring said valve ( 5 );   an oil-chamber ( 10 ) having a release-valve ( 11 );   a plunger ( 12 ) slidably fitted into said oil-chamber ( 10 ), said plunger ( 12 ) being linked or embodied to said cam-follower valve-actuator assembly ( 6 );   a control unit ( 13 ) for controlling said release-valve ( 11 ), characterized in that:   the valve opens following substantially the theoretical opening valve lift pattern;   the plunger, pressed by oil trapped into the oil-chamber, retards the restoring of the valve so that the valve closes controllably retarded relative to the theoretical closing valve lift pattern, according the state of the release-valve.   
     
     
         2 . A variable valve actuation system according  claim 1   characterized in that during the valve closing, the plunger progressively covers an opening of the oil-chamber through which oil escapes, so that the damping action of the oil increases, so that the valve closes smoothly, quietly, without bouncing and in time.   
     
     
         3 . A variable valve actuation system according  claim 1  wherein the oil pressure into the oil-chamber during the valve closing is substantially higher than the oil pressure into the oil-chamber during the valve opening. 
     
     
         4 . A variable valve actuation system according  claim 1  wherein the release-valve is an on-off solenoid valve electronically controlled. 
     
     
         5 . A variable valve actuation system according  claim 1  wherein the release-valve is an analog valve. 
     
     
         6 . A variable valve actuation system according  claim 1  that retards the closing of the valve so that to maintain it open after the bottom dead center until the unnecessary part of the charge that has entered into the cylinder is pushed out by the piston, so that the engine operates controllably at the desirable load. 
     
     
         7 . A variable valve actuation system according  claim 1  that controls the breathing of a variable compression ratio engine in order to provide a substantially variable capacity engine, thereby an engine capable to operate permanently at optimum thermal efficiency. 
     
     
         8 . A variable valve actuation system comprising at least:
 a valve;   a cam dictating a basic restoring pattern for said valve to follow during valve closing;   a hydraulic means resisting to the closing motion of said valve;   an on-off solenoid valve, said hydraulic means applying a strong or a weak resistance to the closing motion of said valve according the state of said on-off solenoid valve,   so that by controlling the timing of the on-off solenoid valve the actual restoring pattern of the valve extends controllably beyond the basic restoring pattern.   
     
     
         9 . A variable valve actuation system according  claim 8  wherein for the smooth landing of the valve on a valve seat, the hydraulic means comprises means that substantially increase its damping action as the valve approaches the valve seat. 
     
     
         10 . A variable valve actuation system comprising at least:
 a cam having an opening contour and a closing contour;   a valve;   a cam-follower valve-actuator assembly for displacing said valve under the camming action of said cam; said cam, said valve and said cam-follower valve-actuator assembly translate said opening contour into a theoretical opening valve lift pattern and said closing contour into a theoretical closing valve lift pattern;   an oil-chamber having a controllable release-valve;   a plunger slidably fitted to said oil-chamber, said plunger pressed by the oil trapped into said oil-chamber retards the valve closing, the valve opening substantially follows the theoretical valve lift pattern, whereas the actual valve closing pattern envelopes the theoretical closing pattern, so that the valve duration is controllably extended.