Engine Braking Method and System

Abstract

An engine braking method includes the steps of engaging a cam roller( 235 ) of an internal combustion engine with an engine power cam( 230 ) for an engine power operation; disengaging the cam roller( 235 ) from the engine power cam( 230 ); losing a motion from the engine power cam( 230 ) and a motion of an engine valve( 301 ) associated with the motion from the engine power cam( 230 ); engaging the cam roller( 235 ) with an engine braking cam( 2302 ) for an engine braking operation; transmitting a motion from the engine braking cam( 2302 ) to the engine valve( 301 ); and generating an engine valve motion for the engine braking operation. An engine braking system includes an engine power cam( 230 ) of an internal combustion engine; an engine braking cam( 2302 ) of the internal combustion engine; and a cam roller( 235 ) that is designed to engage with the engine power cam( 230 ) for an engine power operation and to engage with the engine braking cam( 2302 ) for an engine braking operation.

1 . An engine braking method comprising:
 engaging a cam roller of an internal combustion engine with an engine power cam for an engine power operation;   disengaging the cam roller from the engine power cam;   losing a motion from the engine power cam and a motion of an engine valve associated with the motion from the engine power cam;   engaging the cam roller with an engine braking cam for an engine braking operation;   transmitting a motion from the engine braking cam to the engine valve; and   generating an engine valve motion for the engine braking operation.   
     
     
         2 . The engine braking method according to  claim 1 , wherein the step of engaging the cam roller with the engine power cam includes using an axial cam roller driver to move the cam roller axially on a roller shaft of the engine to a first axial position on the roller shaft, and wherein the step of engaging the cam roller with the engine braking cam includes using the axial cam roller driver to move the cam roller axially on the roller shaft of the engine to a second axial position on the roller shaft. 
     
     
         3 . The engine braking method according to  claim 2 , wherein said axial cam roller driver is integrated into a valve actuator of the engine. 
     
     
         4 . The engine braking method according to  claim 3 , wherein said axial cam roller driver comprises a piston-spring mechanism in the valve actuator, said piston-spring mechanism being engaged with one end of a linkage or a sliding fork, the other end of the linkage or the sliding fork being engaged with the cam roller. 
     
     
         5 . The engine braking method according to  claim 2 , wherein said axial cam roller driver is placed outside of a valve actuator of the engine, said axial cam roller driver moving the cam roller axially on the roller shaft through a linkage or a sliding fork. 
     
     
         6 . The engine braking method according to  claim 2 , wherein said cam roller is designed to have a tendency to separate radially from the cam shaft to enhance the axial motion of the cam roller on the roller shaft. 
     
     
         7 . The engine braking method according to  claim 1 , wherein the engine power cam and the engine braking cam are located on a common cam shaft, are adjacent to each other, and have the same or substantially the same inner base circle. 
     
     
         8 . The engine braking method according to  claim 1 , further comprising a transition mechanism that assists the cam roller to move between the engine power cam and the engine braking cam. 
     
     
         9 . The engine braking method according to  claim 1 , further comprising a transition mechanism, wherein the transition mechanism includes an inclined line or surface transition between a first height on the engine power cam and a second height on the engine braking cam. 
     
     
         10 . The engine braking method according to  claim 1 , wherein the step of engaging the cam roller with the engine power cam includes moving both the engine power cam and the engine braking cam to a first axial position on a camshaft, and wherein the step of engaging the cam roller with the engine braking cam includes moving both the engine power cam and the engine braking cam to a second axial position on the camshaft. 
     
     
         11 . The engine braking method according to  claim 1  , wherein the cam roller is placed on a rocker arm of the engine, and the step of engaging the cam roller with the engine power cam includes moving the rocker arm to a first axial position on a rocker shaft, and wherein the step of engaging the cam roller with the engine braking cam includes moving the rocker arm to a second axial position on the rocker shaft. 
     
     
         12 . The engine braking method according to  claim 1 , wherein said cam roller comprises an exhaust cam roller, said engine power cam comprises a normal exhaust cam, and said engine braking cam comprises a braking exhaust cam. 
     
     
         13 . The engine braking method according to  claim 12 , comprising,
 engaging the exhaust cam roller with the normal exhaust cam for the engine power operation;   disengaging the exhaust cam roller with the normal exhaust cam;   losing a motion from the normal exhaust cam and a motion of an engine exhaust valve associated with the motion from the normal exhaust cam;   engaging the exhaust cam roller with the braking exhaust cam for the engine braking operation; transmitting a motion from the braking exhaust cam to the engine exhaust valve; and   generating an engine exhaust valve motion for the engine braking operation.   
     
     
         14 . The engine braking method according to  claim 12 , wherein said braking exhaust cam comprises three braking exhaust cam lobes, the first braking exhaust cam lobe being the first compression release cam lobe and associated with a location near the engine compression top dead center, the second braking exhaust cam lobe being the second compression release cam lobe and associated with a location near the engine exhaust top dead center, the third braking exhaust cam lobe being the exhaust gas recirculation cam lobe and associated with a location mainly in the engine expansion stroke, immediately following the first compression release cam lobe or directly engaging with the first compression release cam lobe. 
     
     
         15 . The engine braking method according to  claim 1 , wherein said cam roller comprises an exhaust cam roller and an intake cam roller, said engine power cam comprises a normal exhaust cam and a normal intake cam, and said engine braking cam comprises a braking exhaust cam and a braking intake cam. 
     
     
         16 . The engine braking method according to  claim 15 , comprising
 engaging the exhaust cam roller with the normal exhaust cam for the engine power operation, and engaging the intake cam roller with the normal intake cam for the engine power operation; disengaging the exhaust cam roller with the normal exhaust cam, and disengaging the intake cam roller with the normal intake cam;   losing a motion from the normal exhaust cam and a motion of an engine exhaust valve associated with the motion from the normal exhaust cam, and losing a motion from the normal intake cam and a motion of an engine intake valve associated with the motion from the normal intake cam; engaging the exhaust cam roller with the braking exhaust cam for the engine braking operation, and engaging the intake cam roller with the braking intake cam for the engine braking operation;   transmitting a motion from the braking exhaust cam to the engine exhaust valve, and transmitting a motion from the braking intake cam to the engine intake valve; and   generating an engine exhaust valve motion for the engine braking operation, and generating an engine intake valve motion for the engine braking operation.   
     
     
         17 . The engine braking method according to  claim 15 , wherein said braking exhaust cam comprises at least two braking exhaust cam lobes, the first braking exhaust cam lobe being the first compression release cam lobe and associated with a location near the engine compression top dead center, the second braking exhaust cam lobe being the second compression release cam lobe and associated with a location near the engine exhaust top dead center. 
     
     
         18 . The engine braking method according to  claim 15 , wherein said braking intake cam comprises at least two braking intake cam lobes, the first braking intake cam lobe being associated with a location mainly in the engine's intake stroke, and the second braking intake cam lobe being associated with a location mainly in the engine's expansion stroke. 
     
     
         19 . The engine braking method according to  claim 1 , wherein the engine has a valve actuator, said valve actuator comprising a rocker arm and a valve bridge, one end of the rocker arm being engaged with the engine power cam or the engine braking cam through the cam roller, the other end of the rocker arm being over the valve bridge, the two ends of the valve bridge being engaged respectively with an inner valve that is close to the cams and with an outer valve that is away from the cams, wherein said engine braking method further comprises the following steps:
 disengaging the rocker arm from the center of the valve bridge while the connection of the cam roller to the engine power cam is being switched to the engine braking cam,   opening the inner valve by the rocker arm while the outer valve being kept closed, and   transmitting the motion of the engine braking cam to the inner valve, and generating the engine braking operation.   
     
     
         20 . The engine braking method according to  claim 19 , wherein a lost motion mechanism is provided to disengage the rocker arm from the center of the valve bridge, said lost motion mechanism being integrated into the valve actuator. 
     
     
         21 - 41 . (canceled)