Engine valve actuation system and method using reduced pressure common rail and dedicated engine valve

Abstract

A system and method for actuating an engine valve to provide engine braking and/or exhaust gas recirculation using a common source of hydraulic fluid is disclosed. The system receives high pressure hydraulic fluid from a common rail system, such as those used to provide fuel injection. The fluid pressure is reduced before being used to actuate an engine valve for engine braking or EGR. Preferably an engine valve that is dedicated to the engine braking or EGR function is provided in the engine. The dedicated engine braking/EGR valve may be driven by an electromagnetic actuator in an alternative embodiment.

What is claimed is:  
     
         1 . An engine valve actuation system, comprising: 
 a high pressure hydraulic fluid passage;    a high pressure hydraulic fluid source;    a fluid pressure reduction device connected to the hydraulic fluid source through the high pressure hydraulic fluid passage;    a low pressure hydraulic fluid passage;    a hydraulic fluid control valve connected to the fluid pressure reduction device through the low pressure hydraulic fluid passage;    an actuator hydraulic fluid passage; and    an engine valve actuator for actuating an engine valve to produce an engine valve event, the engine valve actuator communicating with the hydraulic fluid control valve through the actuator hydraulic fluid passage.    
     
     
         2 . The system of  claim 1 , wherein the engine valve event is selected from the group consisting of: a compression release braking event, a bleeder braking event, and an exhaust gas recirculation event.  
     
     
         3 . The system of  claim 1 , wherein the hydraulic fluid source comprises a fuel injection system.  
     
     
         4 . The system of  claim 1 , wherein the fluid pressure reduction device reduces the pressure of the hydraulic fluid from a first pressure to a second pressure having a pressure of approximately a magnitude lower than the first pressure.  
     
     
         5 . The system of  claim 4 , wherein the second pressure is approximately 300 psi.  
     
     
         6 . The system of  claim 1 , wherein the control valve comprises: 
 a valve body having a plurality of fluid passages formed therein, the valve body adapted to selectively translate between a first operating position and a second operating position;    a controller for translating the valve body; and    a spring for biasing the valve body into the first operating position.    
     
     
         7 . The system of  claim 6 , wherein the controller translates the valve body at a rate of at least once per engine cycle.  
     
     
         8 . The system of  claim 6 , further comprising an accumulator, wherein the control valve connects the actuator hydraulic fluid passage with the accumulator when the valve body is in the first operating position.  
     
     
         9 . The system of  claim 6 , wherein the control valve connects the actuator hydraulic fluid passage with a low pressure hydraulic fluid tank when the valve body is in the first operating position.  
     
     
         10 . The system of  claim 6 , wherein the control valve connects the actuator hydraulic fluid passage with the low pressure hydraulic fluid passage when the valve body is in the second operating position.  
     
     
         11 . The system of  claim 1 , wherein the engine valve actuator comprises: 
 a fluid chamber for receiving hydraulic fluid from the actuator hydraulic fluid passage;    an actuator piston slidably disposed in the fluid chamber; and    a return spring in contact with the actuator piston.    
     
     
         12 . The system of  claim 1 , further comprising: 
 a low pressure hydraulic fluid tank, and wherein the hydraulic fluid source further comprises: 
 a high pressure pump in communication with the low pressure fluid tank;  
 a pressure regulator; and  
 a high pressure plenum connected to the high pressure hydraulic fluid passage.  
   
     
     
         13 . The system of  claim 1 , wherein the engine valve is a dedicated engine exhaust valve.  
     
     
         14 . The system of  claim 1 , wherein the engine valve requires less force to actuate it than a main exhaust valve.  
     
     
         15 . An engine valve actuation system, comprising: 
 a high pressure hydraulic fluid source for providing hydraulic fluid at a first pressure;    a fluid pressure reduction device connected to the hydraulic fluid source;    a hydraulic fluid control valve connected to the fluid pressure reduction device having a first operating position and a second operating position; and    an engine valve actuator for actuating an engine valve to produce an engine valve event adapted to receive the hydraulic fluid at a second pressure when the hydraulic fluid control valve is in the second operating position.    
     
     
         16 . The system of  claim 15 , wherein the second pressure is approximately 300 psi.  
     
     
         17 . A method of actuating an engine valve in an internal combustion engine to produce an engine valve event, the method comprising the steps of: 
 providing hydraulic fluid to a fluid pressure reduction device;    reducing the pressure of the hydraulic fluid from a first pressure to a second pressure;    selectively applying the hydraulic fluid at the second pressure to an engine valve actuator; and    actuating the engine valve to produce the engine valve event.    
     
     
         18 . The method of  claim 17 , wherein the step of actuating the engine valve further comprises the step of producing a compression release braking event.  
     
     
         19 . The method of  claim 17 , wherein the step of actuating the engine valve further comprises the step of producing a bleeder braking event.  
     
     
         20 . The method of  claim 17 , wherein the step of actuating the engine valve further comprises the step of producing an exhaust gas recirculation event.