Variable engine valve actuator

Abstract

An engine valve actuation system is provided. The system includes an engine valve having a valve element, a rocker arm having a pivot point, a first end, and a second end, and a valve actuator. The valve actuator has a body member having a chamber adapted to receive a fluid, a seat, and a passageway adapted to conduct fluid into and out of the chamber. A piston is slidably disposed in the chamber of the body member and is operatively engaged with the second end of the rocker arm. A control valve is connected to the passageway. The control valve has a first position where fluid is allowed to flow relative to the passageway to allow the body member to move relative to the piston until the seat moves into engagement with the piston to thereby move the piston to pivot the rocker arm and actuate the engine valve. The control valve also has a second position where fluid is prevented from flowing relative to the passageway so that movement of the body member causes a corresponding motion of the piston to pivot the rocker arm and actuate the engine valve while the piston is separated from the seat by an amount of fluid.

What is claimed is:  
     
         1 . An engine valve actuation system, comprising: 
 an engine valve having a valve element;    a rocker arm having a pivot point, a first end, and a second end, the first end of the rocker arm operatively engaged with the engine valve; and    a valve actuator having: 
 a body member having a chamber adapted to receive a fluid, a seat, and a passageway adapted to conduct fluid into and out of the chamber;  
 a piston slidably disposed in the chamber of the body member and operatively engaged with the second end of the rocker arm; and  
 a control valve connected to the passageway and having a first position where fluid is allowed to flow relative to the passageway to allow the body member to move relative to the piston until the seat moves into engagement with the piston to thereby move the piston to pivot the rocker arm and actuate the engine valve, the control valve having a second position where fluid is prevented from flowing relative to the passageway so that movement of the body member causes a corresponding motion of the piston to pivot the rocker arm and actuate the engine valve while the piston is separated from the seat by an amount of fluid.  
   
     
     
         2 . The actuator of  claim 1 , further including a spring acting on the piston to bias the piston away from the seat of the body member.  
     
     
         3 . The actuator of  claim 2 , wherein the spring is disposed in the chamber of the body member.  
     
     
         4 . The actuator of  claim 1 , wherein the body member includes a wall defining the chamber and the passageway is disposed in the wall adjacent the seat.  
     
     
         5 . The actuator of  claim 1 , further including a controller adapted to move the control valve between the first and second positions.  
     
     
         6 . The actuator of  claim 1 , further including a housing having a bore and wherein the body member is slidably disposed in the bore.  
     
     
         7 . The actuator of  claim 6 , wherein the housing includes a second passageway adapted for selective communication with the passageway in the body member.  
     
     
         8 . A method of actuating a valve in an engine, comprising: 
 operating a cam assembly to move a body member between a first position and a second position, the body member having a chamber adapted to slidably receive a piston that is operatively connected to a valve element through a rocker arm;    directing a fluid into the chamber in the body member;    sensing an operating parameter of the engine;    preventing the fluid from leaving the chamber when the sensed operating parameter indicates that the engine is experiencing a first operating condition, the fluid in the chamber linking the body member with the piston so that movement of the body member causes a corresponding motion of the piston to pivot the rocker arm and thereby actuate the valve; and    allowing the fluid to leave the chamber when the sensed operating parameter indicates that the engine is experiencing a second operating condition, the escaping fluid allowing the body member to move relative to the piston until the seat engages the piston to pivot the rocker arm and thereby actuate the valve.    
     
     
         9 . The method of  claim 8 , further including moving a control valve to a first position to allow the fluid to flow relative to a passageway to leave the chamber.  
     
     
         10 . The method of  claim 9 , further including moving the control valve to a second position to prevent fluid from flowing relative to the passageway.  
     
     
         11 . The method of  claim 8 , wherein the first operating condition is one of a first set of operating conditions and the second operating condition is one of a second set of operating conditions.  
     
     
         12 . An engine system, comprising: 
 a cam shaft;    a cam assembly operatively connected to the cam shaft and adapted to rotate with the cam shaft;    an engine block defining a cylinder having a combustion chamber;    a cylinder head defining a first passageway connecting one of an intake manifold and an exhaust manifold with the combustion chamber;    an engine valve having a valve element disposed in the first passageway and moveable between a first position where the valve element prevents a flow of fluid relative to the first passageway and a second position where the valve element allows a flow of fluid relative to the first passageway;    a rocker arm having a pivot point, a first end, and a second end, the first end of the rocker arm operatively engaged with the engine valve; and    a valve actuator having: 
 a body member having a chamber adapted to receive a fluid, a seat, and a second passageway adapted to conduct fluid into and out of the chamber;  
 a piston slidably disposed in the chamber of the body member and operatively engaged with the second end of the rocker arm; and  
 a control valve connected to the second passageway and having a first position where fluid is allowed to flow relative to the second passageway to allow the body member to move relative to the piston until the seat moves into engagement with the piston to thereby move the piston to pivot the rocker arm and move the engine valve towards the second position, the control valve having a second position where fluid is prevented from flowing relative to the second passageway so that movement of the body member causes a corresponding motion of the piston to pivot the rocker arm and move the engine valve towards the second position while the piston is separated from the seat by an amount of fluid.  
   
     
     
         13 . The engine of  claim 12 , further including a valve spring acting on the valve element to move the valve element towards the first position.  
     
     
         14 . The engine of  claim 12 , further including a spring acting on the piston to move the piston away from the seat of the body member.  
     
     
         15 . The engine of  claim 12 , wherein the body member includes a wall defining the chamber and the passageway is disposed in the wall adjacent the seat.  
     
     
         16 . The engine of  claim 12 , further including a controller adapted to move the control valve between the first and second positions.  
     
     
         17 . The engine of  claim 16 , further including a sensor adapted to sense an operating parameter of the engine and wherein the controller moves the control valve to the first position when the sensed operating parameter indicates that the engine is operating in one of a first set of operating conditions.  
     
     
         18 . The engine of  claim 17 , wherein the controller moves the control valve to the second position when the sensed operating parameter indicates that the engine is operating in one of second set of operating conditions.  
     
     
         19 . The engine of  claim 12 , wherein the cam assembly includes a cam lobe adapted to move the body member from the first position to the second position.  
     
     
         20 . The engine of  claim 19 , wherein the cam lobe is configured to move the seat of the body member into engagement with the piston to move the piston and the valve element towards the second position when the control valve is in the first position.  
     
     
         21 . The engine of  claim 19 , wherein the cam lobe is configured such that the seat of the body member does not engage the piston when the control valve is in the first position.  
     
     
         22 . The engine of  claim 12 , wherein the valve element is an exhaust valve and wherein the cam assembly is adapted to open the exhaust valve when the piston is moving through an exhaust stroke when the control valve is in the first position, the cam assembly being further adapted to open the exhaust valve when the piston is moving through the exhaust stroke and when the piston is at or near a top dead center position of a compression stroke when the control valve is in the second position.  
     
     
         23 . The engine of  12 , wherein the valve actuator further includes a housing having a bore and wherein the body member is slidably disposed in the bore.  
     
     
         24 . The engine of  claim 23 , wherein the housing includes a second passageway adapted for selective communication with the passageway in the body member.