An actuation apparatus and methods of operation thereof

Abstract

A rotary electromagnetic actuator includes a biasing assembly for applying a torque to its rotor. Such an actuator may be used to operate a poppet valve of an internal combustion engine. The biasing assembly is moveable between a first configuration and a second configuration, wherein the biasing assembly stores a higher amount of potential energy in its second configuration than in its first configuration. The apparatus includes a latching mechanism for selectively latching the biasing assembly in its second configuration.

1 . An actuation apparatus having an electromagnetic actuator comprising:
 a stator;   a rotor which is rotatable relative to the stator over a range of rotation of the rotor; and   a biasing assembly for applying a torque to the rotor over at least part of the range of rotation of the rotor,   wherein the biasing assembly is moveable between a first configuration and a second configuration, wherein the biasing assembly stores a higher amount of potential energy in its second configuration than in its first configuration, and   the apparatus includes:   a latching mechanism for selectively latching the biasing assembly in its second configuration.   
     
     
         2 . The apparatus of  claim 1 , wherein the apparatus includes a controller which is operable to control the latching mechanism to latch the biasing assembly in its second configuration during an oscillation of the rotor and to release the biasing assembly from its second configuration after the oscillation. 
     
     
         3 . The apparatus of  claim 1 , wherein the apparatus includes a controller which is operable to control the latching mechanism to latch the biasing assembly in its second configuration during a full rotation of the rotor and to release the biasing assembly from its second configuration after the full rotation. 
     
     
         4 . The apparatus of  claim 1 , wherein the biasing assembly comprises a resilient mechanical component. 
     
     
         5 . The apparatus of  claim 1 , wherein the rotor defines a cam surface and the biasing assembly includes a cam follower in engagement with the cam surface, and the magnitude of the potential energy stored by the biasing assembly is dependent on the magnitude of the displacement of the cam follower by the cam surface. 
     
     
         6 . The apparatus of  claim 1 , wherein the latching mechanism includes a latch member which is moveable between a first position in which the latch member retains the biasing assembly in its second configuration and a second position where the latch member does not impede movement of the biasing assembly between its first and second configurations. 
     
     
         7 . The apparatus of  claim 6 , wherein the latching mechanism is arranged to selectively apply a resilient biasing force to the latch member which urges the latch member towards its first position. 
     
     
         8 . The apparatus of  claim 6 , wherein the rotor defines a cam surface and the biasing assembly includes a cam follower in engagement with the cam surface, and the magnitude of the potential energy stored by the biasing assembly is dependent on the magnitude of the displacement of the cam follower by the cam surface, wherein the latch member restricts movement of the cam follower when the latch member is in its first position. 
     
     
         9 . The apparatus of  claim 8 , wherein the cam follower is mounted for rotation about a pivot, the cam follower includes a profiled portion which extends radially outwardly away from the pivot, and when the latch member is in its first position, it engages with the profiled portion and prevents rotation of the profiled portion around the pivot in at least one direction. 
     
     
         10 . A combination of the apparatus of  claim 6  and a further electromagnetic actuator, wherein the latch member is moveable between a first position in which the latch member retains the biasing assemblies of both actuators in their second configurations and a second position where the latch member does not impede movement of the biasing assemblies between their first and second configurations. 
     
     
         11 . The combination of  claim 10 , wherein the biasing assembly of each actuator includes a cam follower, and the cam followers are mounted for rotation about a common pivot. 
     
     
         12 . The combination of  claim 11 , wherein each cam follower includes a profiled portion which extends radially outwardly away from the pivot, and when the latch member is in its first position, it engages with each profiled portion and prevents rotation of each profiled portion around the pivot in at least one direction. 
     
     
         13 . An internal combustion engine including at least one cylinder having at least one valve and the actuation apparatus of  claim 1 , wherein the actuator is arranged to actuate the at least one valve. 
     
     
         14 . An internal combustion engine including at least one cylinder having at least two valves and the combination of  claim 10 , with each of the actuators arranged to actuate a respective valve. 
     
     
         15 . A method of operating an electromagnetic actuator comprising:
 a stator;   a rotor which is rotatable relative to the stator over a range of rotation of the rotor; and   a biasing assembly for applying a torque to the rotor over at least part of the range of rotation of the rotor,   wherein the biasing assembly is moveable between a first configuration and a second configuration, wherein the biasing assembly stores a higher amount of mechanical potential energy in its second configuration than in its first configuration,   the method comprising the step of selectively latching the biasing assembly in its second configuration.   
     
     
         16 . The method of  claim 15 , wherein the biasing assembly is latched in its second configuration during an oscillation of the rotor and the method comprises a further step of releasing the biasing assembly from its second configuration after the oscillation. 
     
     
         17 . The method of  claim 15 , wherein the biasing assembly is latched in its second configuration during a full rotation of the rotor and the method comprises a further step of releasing the biasing assembly from its second configuration after the full rotation. 
     
     
         18 . The method of  claim 15 , wherein the actuator is arranged to actuate a valve of a cylinder in an internal combustion engine. 
     
     
         19 . The method of  claim 18 , wherein the biasing assembly is latched in its second configuration during a first cycle of opening and closing of the valve, and released from its second configuration during a second, subsequent cycle of opening and closing of the valve.