Position sensing device and method

• US 20060017431A1
• Filed: 07/21/2004
• Published: 01/26/2006
• Est. Priority Date: 07/21/2004
• Status: Active Grant

• Current Assignee: Control Products Incorporated (Emerson Electric Company)
• Original Assignee: Richard O. Glasson
• Inventors: Glasson, Richard O.
• Granted Patent: US 7,609,055 B2
• Time in Patent Office: Days
• US Class Current: 324/207.150
• CPC Class Codes: G01D 2205/772 Sawtooth profiles
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other

Abstract

A field-altering device for an inductive sensor has an elongated body with a substantially saw-tooth profile. The body is made of steel or other type ferrous material. With use in a Hall-effect sensor, the body moves relative to the sensor causing the field to vary periodically with time. The sensor generates an electrical signal in dependence on the field variations, the electrical signal having a saw-tooth pattern.

Claims

1. A sensing device comprising:

at least one inductive sensor; and

a body moveable relative to said sensor, said body comprised of a material capable of altering a magnetic field, said body further having a surface with a substantially saw tooth profile in a direction of relative travel between said body and said inductive sensor.

2. A device in accordance with claim 1 wherein said at least one inductive sensor is a magnetic effect sensor.

3. A device in accordance with claim 2 wherein said at least one magnetic effect sensor is a Hall sensor.

4. A device in accordance with claim 1 wherein said body comprises a ferrous material.

5. A device in accordance with claim 1 wherein said body is at least partially cylindrical in shape with said saw tooth profile disposed along an axial length of said cylindrical body.

6. A device in accordance with claim 1 wherein said saw tooth profile includes at least two conical sections in said saw tooth profile.

7. A device in accordance with claim 6 wherein at least two of said conical sections have substantially uniform slope angles.

8. A device in accordance with claim 7 wherein at least two of said conical sections have a substantially uniform length in the direction of travel.

9. A device in accordance with claim 6 wherein said saw tooth pattern sections possesses at least two different slope angles within at least one particular region of movement requiring greater relative position precision relative to regions requiring lesser relative position precision.

10. A device in accordance with claim 1 further comprising at least one magnet disposed to provide said magnetic field wherein movement of the body relative to said sensor creates a time-varying magnetic field, said sensor operable to provide an output signal in dependence on said time-varying magnetic field.

11. A device in accordance with claim 1 further comprising at least another magnet, said at least one magnet and at least another magnet arranged in a push-pull configuration.

12. A device in accordance with claim 1 further comprising a processor responsive to signals from the at least one sensor, and instructions for instructing the processor to carry out steps in response to the signals.

13. A device in accordance with claim 12 further comprising at least another sensor, wherein the processor causes a sensing function to alternate between the at least one sensor and the at least another sensor.

14. A device in accordance with claim 11, wherein said saw tooth profile includes at least two conical sections in said saw tooth profile, each said segment having a predetermined length value and slope angle value accessible to the processor, the instructions including instructions for comparing the predetermined length value to a measured length value for the conical sections and to adjust the slope angle value in response to the comparison.

15. A device in accordance with claim 13 wherein the at least one sensor and the at least another sensor are disposed in offset relation.

25. A device in accordance with claim 1 wherein the body rotatably moves relative to the at least one inductive sensor.

16. A sensing device comprising:

a first inductive sensor and a second inductive sensor disposed in offset relation to each other;

a body moveable relative to said sensors, said body comprising a material capable of altering a magnetic field, wherein the sensors and the body are disposed in the magnetic field, said body further having a surface profile capable of causing a time dependent variation to the magnetic field when said body moves relative to said sensors;

a substantially magnetically permeable envelope enclosing at least a portion of said body; and

processing circuitry responsive to outputs of the sensors.

17. A device in accordance with claim 16 wherein said body profile includes a region having at least two repeated profile patterns.

18. A device in accordance with claim 17 wherein said repeated profile pattern is a saw tooth pattern.

19. A device in accordance with claim 17 wherein said repeated profile pattern is a substantially sinusoidal pattern.

20. A device in accordance with claim 16 wherein said inductive sensor is a magnetic effect sensor.

21. A device in accordance with claim 20 wherein said magnetic effect sensor is a Hall sensor.

22. A method for generating a time varying field coupled to an inductive sensor comprising the steps of:

moving an elongated body relative to the inductive sensor, the body comprised of a material capable of altering a magnetic field and having a profile including a portion defining an angle with an axis of the elongated body, the angle having a magnitude of less than 90 degrees.

23. A field altering device for an inductive sensor comprising:

an elongated body comprised of a material capable of altering a magnetic field and having a periodic profile over at least a portion thereof; and

a magnetically permeable envelope enclosing at least a portion of said elongated body.

24. A field altering device in accordance with claim 23 wherein each period includes a portion defining an angle with an axis of the elongated body, the angle having a magnitude of less than 90 degrees.