Rotary Single-Phase Electromagnetic Actuator

Abstract

A single phase, rotary electromagnetic actuator comprising first and second stator assemblies, located in oppositely facing spaced apart positions along a common central axis, permits a magnetized disc magnet rotor to rotate about the common axis free of any magnetic attractive forces normally tending to move the disc magnet longitudinally along the axis, or alternatively to be located in a position to create a desired longitudinal attractive force. The entire assembly is maintained in operative positions by a circular belt which provides an inward facing lip on each side of which the stator assemblies are seated and which determines the magnetic airgap spacing for the disc. The invention may be implemented as a servo-actuator by the inclusion of an angular position sensor that uses the actuator rotor as the magnetic field emitter, and a receiver for the magnetic field and its contacts, located in the belt lip.

1 - 22 . (canceled) 
     
     
         23 . A rotary single-phase electromagnetic actuator comprising:
 two stators with at least one of those stators being an active stator for generating a magnetic field, the active stator having a stator structure with two stator poles having two opposed inner surfaces extending to a base and said other stator having two stator poles extending to a base, said two stator poles configured for single-phase activation, the two stators being axially spaced apart a predetermined distance defining an airgap;   an inertia assembly comprising:
 a shaft defining an axis; 
 a disc magnet rotor absent a yoke of high permeability magnetic material mounted on the shaft for rotating the shaft, the rotor magnet being axially magnetized with a plurality of pole pairs of alternating polarity; 
   the rotor being in the airgap and spaced from each stator by a predetermined distance;   wherein the two stators are configured and positioned relative to one another so as to establish, when said at least one active stator is energized, a closed-loop magnetic flux circuit that flows between the two stators through the stator poles, said base of the active stator, said base of the other stator and the rotor, and   wherein the interaction between the rotor's magnetic field and the magnetic fields of said stators is capable of generating a torque delivered to the shaft so as to produce an angular stroke of equal to or less than 180 degrees.   
     
     
         24 . The actuator of  claim 23 , wherein said actuator is configured such that the shaft provides an angular stroke over a range of angles at a substantially constant torque. 
     
     
         25 . The actuator of  claim 23 , wherein the actuator exhibits a figure of merit (AK) of at least 1000, wherein 
       
         
           
             
               
                 AK 
                 = 
                 
                   
                     K 
                     m 
                     2 
                   
                   
                     J 
                     m 
                   
                 
               
               , 
             
           
         
         wherein, 
       
       
         
           
             
               
                 
                   K 
                   m 
                 
                 = 
                 
                   T 
                   
                     W 
                   
                 
               
               , 
             
           
         
         where T represents the actuator's output torque and W represents the input power, and 
         J m  is the sum of the rotor's inertia and the shaft's inertia. 
       
     
     
         26 . The actuator of  claim 23 , wherein one of the two stators is an active stator on one side of the rotor and the other stator is a passive stator on the other side of the rotor. 
     
     
         27 . The actuator of  claim 23 , wherein each of said two stators is an active stator and said closed-loop magnetic flux circuit is established upon activation of both of said active stators. 
     
     
         28 . The actuator of  claim 23 , wherein said at least one active stator exhibits a U-shaped cross section extending between two spaced apart poles so as to generate U-shaped magnetic flux lines. 
     
     
         29 . The actuator of  claim 23 , further comprising a magnetic position sensor receiver disposed relative to the rotor so as to be sensitive to magnetic flux generated upon rotation of the rotor and wherein the rotor is configured such that a distance between the rotor and the magnetic position sensor varies as the rotor rotates. 
     
     
         30 . The actuator of  claim 23 , wherein the rotor is positioned closer in the airgap to one stator than to the other stator. 
     
     
         31 . The actuator of  claim 23 , wherein said actuator is configured such that the shaft provides an angular stroke in a range of 50 degrees to 130 degrees. 
     
     
         32 . The actuator of  claim 23 , wherein said actuator is configured such the shaft provides an angular stroke in a range of 60 degrees to 110 degrees. 
     
     
         33 . The actuator of  claim 23 , further comprising stator assemblies in which said stators are incorporated and further comprising a nonmagnetic belt having an inward facing lip with first and second space-defining edge surfaces spaced apart a predetermined distance and the first and second space-defining edge surfaces being in contact with the stator assemblies on each side of the rotor to define said axial airgap between the stators. 
     
     
         34 . The actuator of  claim 23 , wherein said disc rotor is attached to the shaft via a coupling member for applying its rotation to the shaft, thereby delivering said torque to the shaft. 
     
     
         35 . The actuator of  claim 23 , wherein each of said stators comprises a high permeability ferromagnetic structure. 
     
     
         36 . The actuator of  claim 23 , wherein said actuator is configured such the torque delivered to the shaft is proportional to a current applied to said at least one active stator. 
     
     
         37 . The actuator of  claim 23 , wherein the poles of said at least one active stator are wound with wire such that said poles exhibit alternating magnetic polarity, when said at least one active stator is energized. 
     
     
         38 . The actuator of  claim 23 , wherein each of said two stators is an active stator and the two stators are configured such that the rotor experiences, when said stators are energized, a greater axial force in the direction of one of the stators than in direction of the other stator. 
     
     
         39 . The actuator of  claim 38 , wherein a surface area of the poles of one of said active stators is greater than a respective surface area of the poles of the other active stator such that said rotor experiences said greater axial force in the direction of the stator having poles with the greater surface area.