Compact robust linear position sensor

• US 20080284554A1
• Filed: 05/14/2007
• Published: 11/20/2008
• Est. Priority Date: 05/14/2007
• Status: Abandoned Application

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Schroeder, Thaddeus, Omekanda, Avoki
• Application Number:
  US11/803,236
• Publication Number:
  US 20080284554A1
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01D 5/2053 by a movable non-ferromagnetic conductive element
• CPC Class Codes: H01F 21/10 by means of a movable shield
• CPC Class Codes: H01F 27/2804 Printed windings

Abstract

The present invention is directed to a position sensor, comprising a printed circuit board; a pair of stationary planar air-core coils formed in a trapezoidal or rectangular shape and side-by-side one another on the printed circuit board, coil windings being relatively uniformly distributed over a predetermined area of the printed circuit board; and a moving target formed by a sheet of copper on the printed circuit board.

Claims

1. A position sensor comprising:

a first printed circuit board;

a pair of stationary planar air-core coils, each formed in a substantially trapezoidal shape and side-by-side one another on the printed circuit board, such that the periphery of the combined pair of side-by-side coils defines a substantially rectangular shape, having coil windings relatively uniformly distributed over a predetermined area of the printed circuit board; and

a movable target formed by a sheet of copper on a second printed circuit board proximate to the first printed circuit board.

2. The position sensor according to claim 1, wherein the coil windings are constructed and arranged to effect substantially constant inductance per unit of area.

3. The position sensor according to claim 1, comprising a third printed circuit board comprising a pair of coils, wherein the first and third circuit boards are disposed one above the other separated by a gap and the target is constrained to move within the gap.

4. The position sensor according to claim 3, wherein the coil pairs are substantially mirror images of each other.

5. The position sensor according to claim 3, wherein the target comprises a two-sided printed circuit board with a copper pattern on each face.

7. A position sensor according to claim 3, wherein the sensor is constructed and arranged to be substantially insensitive to air gap variation.

9. The position sensor according to claim 3, wherein coils of each pair corresponding to a given direction of inductance change for a given direction of target movement are electrically combined.

10. A position sensor according to claim 9, wherein the combination of coil pairs are combined in series or in parallel.

11. The position sensor according to claim 3, wherein the coil pairs are electrically connected in a bridge configuration and coils corresponding to a given direction of inductance change for a given direction of target movement are disposed in non-adjacent legs of the bridge circuit.

6. (canceled)

8. (canceled)

12. A position sensing system comprising:

A first printed circuit board;

a pair of stationary planar air-core coils, each formed in a substantially trapezoidal shape and side-by-side one another on the printed circuit board, such that the periphery of the combined pair of side-by-side coils defines a substantially rectangular shape, having coil windings relatively uniformly distributed over a predetermined area of the printed circuit board;

a movable target formed by a sheet of copper, said target constrained to move along an axis separated from and substantially parallel to the plane of the circuit board, said target disposed such that a projection of said target onto said coils covers the combined width of said coils in a direction transverse to the axis of motion of said movable target, wherein said coils and said target cooperate to effect an increase in inductance of one coil and a decrease in inductance in the other coil in the coil pair when the target is moved in a direction along the axis of motion;

said coil pair connected electrically in series, with a source of alternating current connected to supply current through the series combination of coils; and

a circuit comprising a precision rectifier or peak detector disposed to convert a signal derived from the interconnection point of the series connected coils into an output voltage.