Dielectric Sensor Arrangement and Method for Swashplate Angular Position Detection

Abstract

Swashplate angle sensing arrangement for a variable displacement pump a nonrotating swashplate and a rotating pump barrel includes a dielectric sensor in a swashplate angle sensing arrangement. The arrangement includes a sensing probe coupled to the casing, a sensor target coupled to the swashplate, and a controller configured to direct an alternating current through the sensing probe to establish an impedance between the probe and the target, and to determine voltage across the probe. The controller is further adapted to determine the angle of the swashplate relative to the casing based on the determined voltage.

I claim: 
     
         1 . A swashplate angle sensing arrangement for a variable displacement pump having a casing containing a nonrotating swashplate adapted to pivot relative to an axis of rotation of a pump barrel, the swashplate defining a swashplate angle relative to a plane substantially perpendicular to the axis of rotation of the pump barrel, the swashplate angle sensing arrangement comprising:
 a sensing probe coupled to the casing;   a sensor target coupled to the swashplate; and   a controller configured to direct an alternating current through the sensing probe to establish an impedance between the sensing probe and the sensor target, and to determine a voltage across the sensing probe, the controller further adapted to determine the angle of the swashplate relative to the casing based on the determined voltage.   
     
     
         2 . The swashplate angle sensing arrangement of  claim 1 , wherein the sensing probe includes a conductive portion exposed to an interior of the casing and a nonconductive portion disposed between the conductive portion and the casing. 
     
     
         3 . The swashplate angle sensing arrangement of  claim 2 , wherein the conductive portion includes a wire. 
     
     
         4 . The swashplate angle sensing arrangement of  claim 1  wherein the sensor target includes a conductive portion and a nonconductive portion disposed between the conductive portion and the swashplate. 
     
     
         5 . The swashplate angle sensing arrangement of  claim 1 , further including fluid media between the sensing probe and the sensor target. 
     
     
         6 . The swashplate angle sensing arrangement of  claim 1  wherein the controller is configured to direct the alternating current between the sensing probe and the casing. 
     
     
         7 . The swashplate angle sensing arrangement of  claim 6  wherein the established impedance changes as the angle of the swashplate changes. 
     
     
         8 . The swashplate angle sensing arrangement of  claim 1  wherein the established impedance changes as the angle of the swashplate changes. 
     
     
         9 . The swashplate angle sensing arrangement of  claim 7  wherein the sensing probe includes a conductive portion exposed to an interior of the casing and a nonconductive portion disposed between the conductive portion and the casing, the sensor target includes a conductive portion and a nonconductive portion disposed between the conductive portion and the swashplate, and fluid media between the sensing probe and the sensor target. 
     
     
         10 . A variable displacement pump, comprising:
 a casing;   a barrel disposed within the casing and adapted to rotate about an axis of rotation;   a nonrotating swashplate disposed in the casing and adapted to pivot relative to the axis;   a sensor target coupled to the swashplate;   a sensing probe coupled to the casing and proximate the sensor target; and   a controller configured to direct a current across the sensing probe to establish an impedance between the sensing probe and the sensor target, and to determine a voltage across the sensing probe, the controller further adapted to determine an angle of the swashplate based on the determined voltage.   
     
     
         11 . The variable displacement pump of  claim 10  further including fluid media disposed between the sensor target and the sensing probe. 
     
     
         12 . The variable displacement pump of  claim 10 , wherein the sensing probe is sealed within the casing. 
     
     
         13 . The variable displacement pump of  claim 10 , wherein the sensing probe includes a conductive portion exposed to an interior of the casing and a nonconductive portion disposed between the conductive portion and the casing. 
     
     
         14 . The variable displacement pump of  claim 10 , wherein the angle of the swashplate is determined relative to a plane substantially perpendicular to the axis of rotation. 
     
     
         15 . The variable displacement pump of  claim 10  wherein the sensor target includes a conductive portion and a nonconductive portion disposed between the conductive portion and the swashplate. 
     
     
         16 . The variable displacement pump of  claim 10  wherein the established impedance changes as the angle of the swashplate changes. 
     
     
         17 . A method for monitoring an angle of a nonrotating swashplate disposed to pivot relative to an axis in a variable displacement pump comprising:
 directing an alternating current across a sensing probe coupled to a casing of the pump to establish an impedance between the sensing probe and a sensor target coupled to the swashplate;   determining a voltage across the sensing probe; and   determining the angle of the swashplate based upon the determined voltage.   
     
     
         18 . The method of  claim 17  wherein directing an alternating current includes directing an alternating current across the sensing probe to establish an impedance between the sensing probe through fluid media disposed between the sensing probe and the sensor target. 
     
     
         19 . The method of  claim 18  wherein the sensing probe includes a conductive portion exposed to an interior of the casing and a nonconductive portion disposed between the conductive portion and the casing, the sensor target includes a conductive portion and a nonconductive portion disposed between the conductive portion and the swashplate, and the fluid media is hydraulic fluid. 
     
     
         20 . The method of  claim 17  further including changing the angle of the swashplate based upon the determined angle.