Solenoid actuator

Abstract

A short travel solenoid actuator ( 44 ) is disclosed which comprises at least one pole piece ( 47, 48 ), an armature ( 51 ), an electromagnet coil ( 46 ) arranged, in response to energisation, to actuate the armature between first and second positions. A permanent magnet ( 52 ) is positioned and orientated so as to latch the armature in the first and second positions when the armature is in the first and second positions respectively. A spring ( 53 ) is arranged to bias the armature.

1 . (canceled) 
     
     
         2 . A method of operating a fuel injector which comprises a solenoid actuator comprising at least one pole piece, an armature, an electromagnet coil arranged, in response to energisation, to cause travel of the armature from a first, closed position towards a second, fully-open position, a permanent magnet positioned and orientated so as to magnetically latch the armature in the first and second positions when the armature is in the first and second positions respectively and a spring arranged to bias the armature and configured to provide sufficient force so as to prevent the armature from latching in the second position, the method comprising:
 using closed-loop control.   
     
     
         3 . A method according to  claim 2 , wherein using the closed-loop control comprises:
 using closed-loop position control.   
     
     
         4 . A method according to  claim 2 , wherein using the closed loop control is used to control partial opening of the fuel injector. 
     
     
         5 . A method according to  claim 2 , wherein using the closed-loop position control comprises:
 using a flux measurement loop.   
     
     
         6 . A method according to  claim 2 , wherein the closed loop control is usable to supress bounce by slowing the armature before contact with at least one end stop. 
     
     
         7 . A method according to  claim 2 , wherein current is passable in the electromagnet coil in either of two directions. 
     
     
         8 . A method according to  claim 3 , wherein using the closed loop position control is used to control a variable valve lift of the fuel injector.