Variable valve actuation

Abstract

A variable valve actuation mechanism actuates a valve of an internal combustion engine. The mechanism includes an actuator with a housing and a piston each moveable along a longitudinal axis in the engine. A cavity is defined between the piston and the housing. A body of fluid is disposed in the cavity and in the reservoir. A fluid passage has an open position wherein the cavity and reservoir are in fluid communication and a closed position wherein the cavity is sealed. When the passage is closed, the housing and piston move generally together. When the passage is open, fluid may pass from the cavity to the reservoir and movement of the housing relative to the piston changes the volume of the cavity.

1 . A variable valve actuation mechanism for actuating a valve of an internal combustion engine, the variable valve actuation mechanism comprising: 
 an actuator including a housing and a piston each movable along a longitudinal axis in the engine for actuating the valve, a cavity being defined between the piston and the housing;    a reservoir;    a body of fluid disposed in the cavity and in the reservoir;    a fluid passage having an open position wherein the cavity and the reservoir are in fluid communication and a closed position wherein the cavity is sealed;    wherein when the passage is closed and the cavity is sealed, the housing and the piston move generally together; and    wherein when the passage is open, fluid may pass from the cavity to the reservoir, and movement of the housing relative to the piston changes the volume of the cavity.    
   
   
       2 . A variable valve actuation mechanism according to  claim 1 , further including a biasing member disposed between the housing and the piston, the biasing member biasing the housing and piston away from each other.  
   
   
       3 . A variable valve actuation mechanism according to  claim 1 , wherein the reservoir comprises a pressurized supply of engine oil.  
   
   
       4 . A variable valve actuation mechanism according to  claim 1 , wherein the reservoir is in fluid communication with a pressurized supply of engine oil.  
   
   
       5 . A variable valve actuation mechanism according to  claim 1 , wherein the reservoir is at least partially filled with a gas that serves as a gas spring.  
   
   
       6 . A variable valve actuation mechanism according to  claim 1 , wherein the housing and the piston are both generally cylindrical.  
   
   
       7 . A variable valve actuation mechanism according to  claim 1 , wherein the housing includes a roller for interaction with a cam lobe.  
   
   
       8 . A variable valve actuation mechanism according to  claim 1 , wherein the housing has a bore defined therein, the piston being slidably received in the bore.  
   
   
       9 . A variable valve actuation mechanism according to  claim 1 , wherein the bore in the housing and the piston are both generally cylindrical.  
   
   
       10 . A variable valve actuation mechanism according to  claim 1 , further including a cam shaft with a cam lobe rotatable about a rotational axis, the cam lobe being in mechanical communication with the housing for actuating the housing in a reciprocating manner along the longitudinal axis, the cam being movable in a direction transverse to the rotational axis to cause a corresponding shift in the midpoint of travel of the housing.  
   
   
       11 . A variable valve actuation system comprising: 
 a cam shaft with a cam lobe, the shaft being rotatable about a rotational axis;    a tappet support with a receiving area defined therein, the receiving area having an inner surface with a fluid supply opening defined therein;    a fluid supply in fluid communication with the supply opening;    a valve movable between an open and a closed position;    a variable valve actuator having a first and a second end, the actuator comprising; 
 a housing defining the first end of the actuator;  
 a piston defining the second end of the actuator;  
 a cavity defined between the housing and piston;  
 the actuator having an outer surface with an opening defined therein, the opening being in fluid communication with the cavity, the actuator being received in the receiving area with the outer surface of the actuator adjacent the inner surface of the receiving area;  
   one of the ends of the actuator being in mechanical communication with the cam lobe and the other of the ends being in mechanical communication with the valve;    the variable valve actuator having a first position wherein the opening in the outer surface is in fluid communication with the opening in the inner surface of the receiving area such that the cavity is in fluid communication with the fluid supply, wherein when the actuator is in the first position fluid may pass between the cavity and the supply such that movement of the housing relative to the piston changes the volume of the cavity; and    the variable valve actuator having a second position wherein the opening in the outer surface is not in fluid communication with the opening in the inner surface of the receiving area such that the cavity is sealed and the housing and piston move generally together    
   
   
       12 . A variable valve actuation system according to  claim 11 , further including a biasing member disposed between the housing and the piston of the actuator, the biasing member biasing the housing and piston away from each other.  
   
   
       13 . A variable valve actuation system according to  claim 11 , wherein the fluid supply comprises a pressurized supply of engine oil.  
   
   
       14 . A variable valve actuation system according to  claim 11 , wherein the fluid supply includes a reservoir.  
   
   
       15 . A variable valve actuation system according to  claim 14 , wherein the reservoir is at least partially filled with a gas that serves as a gas spring.  
   
   
       16 . A variable valve actuation system according to  claim 11 , wherein the housing and the piston are both generally cylindrical.  
   
   
       17 . A variable valve actuation system according to  claim 11 , wherein the housing includes a roller for interaction with the cam lobe.  
   
   
       18 . A variable valve actuation system according to  claim 11 , wherein the housing has a bore defined therein, the piston being slidably received in the bore.  
   
   
       19 . A variable valve actuation system according to  claim 11 , wherein the bore in the housing and the piston are both generally cylindrical.