Programmable high speed valve actuator and power supply therefor

Abstract

An electromagnetic actuator is described in which a rotor comprising permanent magnet means is rotatable in a stator which is magnetisable by causing an electric current to flow through at least one winding associated with the stator. The rotor has at least two stable rest positions, each defined by spring and/or magnetic forces acting on the rotor. Spring means stores energy during part of the movement of the rotor and provides kinetic energy for accelerating the rotor during subsequent movement thereof away from rest in one position towards another. A magnetic torque is exerted on the rotor when a current flows in said at least one winding which is sufficient to overcome the force(s) holding the rotor in that rest position, to cause the rotor to rotate in a direction from that rest position towards another a rest position. The rotor is connected to a thrust member by a mechanical linkage by which the rotational movement of the rotor is converted into substantially linear movement. The linkage has a mechanical advantage which varies in a predetermined manner during the rotation of the rotor. The actuator can be used to open and close a valve of an internal combustion engine. A power supply is provided for delivering current to the actuator from a current source so as to operate the actuator in an energy efficient manner.