A torque motor ( 20 ) has a base ( 21 ), four polepieces ( 22 A, 22 B, 22 C, 22 D) extending away from the base, the polepieces being separated from one another and being arranged at the corners of an imaginary polygon ( 27 ), each polepiece terminating in a pole ( 23 A, 23 B, 23 C, 23 D); a coil ( 24 A, 24 B, 24 C, 24 D) surrounding each of the polepieces; an armature ( 26 ) pivotally mounted on the base, the armature having a portion arranged to move toward and away from an associated one of the poles, respectively, to define a variable-reluctance air gap (g A , g B , g C , g D ) therebetween; a permanent magnet ( 29 ) mounted on one of the base and armature and polarized in a direction parallel to the pivotal axis of the armature; and wherein at least a portion of the torque motor is formed by a MEMS technique; whereby the coil may be selectively energized to cause the armature to pivot about its axis.
1. A torque motor, comprising:
a base;
four polepieces extending away from said base, said polepieces being separated from one another and being arranged at the corners of an imaginary polygon, each polepiece terminating in a pole;
a coil surrounding one of said polepieces;
an armature pivotally mounted on said base, said armature having a portion arranged to move toward and away from an associated one of said poles to define a variable-reluctance air gap therebetween;
a permanent magnet mounted on one of said base and armature and polarized in a direction substantially perpendicular to the pivotal axis of said armature;
wherein said magnet is mounted on said base, wherein said base has lateral portions formed of a magnetically-permeable material positioned on opposite sides of said magnet, and wherein said magnet is polarized to oppositely polarize said lateral portions; and
wherein at least a portion of said torque motor is formed by a MEMS technique;
whereby said coil may be selectively energized to cause said armature to pivot about said axis.
2. A torque motor as set fort in claim 1 wherein two of said poles are polarized to the polarity of one of said lateral portions, and two of said poles are polarized to the polarity of the other of said lateral portions.
3. A torque motor as set forth in claim 1 wherein said polygon is a rectangle.
4. A torque motor as set forth in claim 3 wherein said rectangle is a square.
5. A torque motor as set forth in claim 1 wherein said poles are substantially coplanar.
6. A torque motor as set forth in claim 1 wherein said armature is arranged as a teeter-totter with respect to said base.
7. A torque motor as set forth in claim 1 and further comprising a centering spring acting between said base and said armature for urging said armature to move toward a position at which the length of said air gaps is substantially equal.
8. A torque motor as set forth in claim 1 wherein the pivotal displacement of said armature will be substantially proportional to the current supplied to said coil.