Reluctance transducer

Abstract

A reluctance transducer includes a soft ferromagnetic yoke and a soft ferromagnetic core element, which is movable relative to the yoke. Two permanent magnets bear the core element. The permanent magnets are arranged relative to each other and to the yoke so that the reluctance transducer has a good linear relationship between displacement and force. The reluctance transducer can be applied as stiffness compensating element. The reluctance transducer can include an electrical winding to allow its application as a magnetic bearing, an actuator or as a displacement, velocity or acceleration sensor with improved intrinsic linearity.

1 . A reluctance transducer comprising:
 a soft ferromagnetic yoke having a first end and a second end, the first end and the second end defining an intermediate space,   a soft ferromagnetic core element partly filling the intermediate space, the core element and the yoke being movable relative to each other in a direction between the first end of the yoke and the second end of the yoke,   a first permanent magnet and a second permanent magnet arranged relative to each other such that the first magnet and the second magnet exert opposite forces on the core element, and   wherein a first pole of the first magnet is mechanically and magnetically coupled by an intermediate soft ferromagnetic element to an equivalent pole of the second magnet,   wherein   a second pole of the first magnet is magnetically insulated from an equivalent pole of the second magnet.   
     
     
         2 . The reluctance transducer according to  claim 1 , wherein the first permanent magnet and the second permanent magnet are arranged such that the direction of a magnetic flux of the first permanent magnet at the first end of the yoke is opposite to the direction of a magnetic flux of the second permanent magnet at the second end of the yoke. 
     
     
         3 . The reluctance transducer according to  claim 1 , wherein the intermediate soft ferromagnetic element is a portion of the yoke. 
     
     
         4 . The reluctance transducer according to  claim 3 , wherein the first end of the soft ferromagnetic yoke is provided with a first cavity receiving the first permanent magnet and the second end of the soft ferromagnetic yoke is provided with a second cavity receiving the second permanent magnet. 
     
     
         5 . The reluctance transducer according to  claim 2 , wherein the yoke comprises a first portion fixed to the first pole of the first magnet and a second portion fixed to the second pole of the first magnet. 
     
     
         6 . The reluctance transducer according to  claim 5 , comprising a third portion of the yoke and wherein the first pole of the second magnet is fixed to the third portion of the yoke and the second portion is fixed to the second pole of the second magnet. 
     
     
         7 . The reluctance transducer according to  claim 2 , wherein the soft ferromagnetic element mechanically coupling the two permanent magnets is a portion of the soft ferromagnetic core element. 
     
     
         8 . The reluctance transducer according to  claim 7 , wherein a first surface of the core element is facing the first end of the yoke and a second surface of the core element is facing the second end of the yoke and wherein the first surface is provided with a cavity receiving the first magnet and the second surface is provided with a cavity receiving the second magnet. 
     
     
         9 . The reluctance transducer according to  claim 3 , wherein the direction from the first end of the yoke to the second end of the yoke is perpendicular to the direction from the first permanent magnet to the second permanent magnet. 
     
     
         10 . The reluctance transducer according to  claim 1 , wherein the soft ferromagnetic yoke has a first portion comprising the first end and the second end, and a second portion that is surrounded by an electrical winding. 
     
     
         11 . The reluctance transducer according to  claim 4 , wherein the soft ferromagnetic yoke has a first portion implemented as a cylinder shell comprising the first end and the second end, and a second portion that is surrounded by an electrical winding, and wherein the second portion includes a cylinder kernel, concentrically arranged with respect to the cylinder shell, the second portion further including intermediate sections magnetically connecting axial ends of the cylinder kernel and cylinder shell, respectively. 
     
     
         12 . The reluctance transducer according to  claim 4 , comprising a multiple number of permanent magnetic pairs, the permanent magnetic elements of each individual pair being arranged opposite to each other near first and second slots, respectively, and magnetically oriented opposite to each other. 
     
     
         13 . The reluctance transducer according to  claim 4 , wherein the core element is formed as a lever moving an actuator element or a sensor element. 
     
     
         14 . The reluctance transducer according to  claim 4 , wherein first and second end portions of the soft magnetic yoke are formed as mutually aligned bars.