Position sensor

• US 20020196015A1
• Filed: 06/21/2001
• Published: 12/26/2002
• Est. Priority Date: 02/01/2000
• Status: Active Grant

• Current Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Cherry GmbH
• Inventors: Zapf, Martin
• Granted Patent: US 6,593,730 B2
• Time in Patent Office: Days
• US Class Current: 324/207.17
• CPC Class Codes: G01D 5/2275 by a movable non-ferromagnetic conductive element
• CPC Class Codes: G01D 5/2291 Linear or rotary variable differential transformers (LVDTs/RVDTs) having a single primary coil and two secondary coils

Abstract

A position sensor for determining a set position thereof is disclosed. The sensor comprises means for generating a time-varying magnetic field, an electrically conductive element positioned such that said time-varying magnetic field generates eddy currents therein and at least one pick-up for generating a signal in response to said time-varying magnetic field. Movement of the conductive element relative to the pick-up alters the magnetic coupling between the field generator and the pick-up allowing the set position to be determined unambiguously.

Claims

1. A position sensor for determining a set position thereof, comprising:

a time-varying magnetic field generator;

an electrically conductive element positioned such that said time-varying magnetic field generates eddy currents therein;

at least one pick-up for generating a signal in response to said time-varying magnetic field; and

a signal processor arranged to receive said signal and to determine the set position of the position sensor,

wherein the conductive element is movable relative to the at least one pick-up such that the signal generated by said pick-up has a magnitude which is dependent on the position of said conductive element, the position of the conductive element corresponding to the set position of the sensor.

2. A position sensor according to claim 1, characterized in that the sensor comprises at least two pick-ups, each of said pick-ups generating a signal in response to said time-varying magnetic field, wherein said signal processor processes the signals from said at least two pick-ups in combination.

3. A position sensor according to claim 2, characterized in that the time-varying magnetic field generator comprises a conductive drive loop and an alternating current generator for passing an alternating current around said drive loop and wherein there are two sensor loops, each arranged within a projected area of said drive loop such that said two drive loops have a combined projected area which is less than the projected area of said drive loop.

4. A position sensor according to claim 3, wherein the drive loop is substantially circular in outline and wherein the two sensor loops each have a projected area in the shape of a sector of a circle, and the conductive element is rotatable relative to the two sensor loops.

5. A position sensor according to claim 4 wherein the projected area of said two sensor loops is substantially equal to two thirds the projected area of said drive loop and wherein said conductive element has a surface which is in the shape of a sector of a circle, substantially equal to the projected area of one sensor loop.

6. A position sensor according to claim 4, wherein the signal processor calculates the sum and the quotient of the pick-up signals to determine an unambiguous sensor position.

7. A position sensor according to claim 1 wherein it is one of a plurality of such sensors multiplexed to a single signal processor.

8. A position sensor according to claim 1 wherein the sensor incorporates an isolation switch.