System and method for detecting an axial position of a shaft

• US 7,280,937 B1
• Filed: 04/18/2006
• Issued: 10/09/2007
• Est. Priority Date: 04/18/2006
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Lenz, James Edward, Greer, Ashley Elwood
• Primary Examiner(s): WACHSMAN, HAL D
• Application Number:
  US11/406,121
• Publication Number:
  US 20070244665A1
• Time in Patent Office: 539 Days
• Field of Search: 702/151
• US Class Current: 702/151
• CPC Class Codes: C23C 8/80 After-treatment
• CPC Class Codes: F15B 15/2846 using detection of markings, e.g. markings on the piston rod
• CPC Class Codes: F15B 15/2861 using magnetic means
• CPC Class Codes: G01D 2205/77 Specific profiles
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A shaft comprises a hardened outer metallic layer having a first hardness level with a generally uniform radial depth. A first strip extends in a generally longitudinal direction in the outer metallic layer. The first strip has a second hardness level different from the first hardness level. A second strip in the outer metallic layer has the second hardness level. The first strip and the second strip are spaced apart from each other over at least a longitudinal region. A sensor senses an angular difference between a first magnetic field associated with the first strip and a second magnetic field associated with the second strip. A data processor references an established relationship between a position of the shaft and the angular difference between magnetic fields associated with the first strip and the second strip to detect a position of the shaft with respect to a reference point.

Claims

1. A method for detecting a position of a shaft, the method comprising:

providing a shaft comprising a hardened outer metallic layer having a first hardness level with a generally uniform radial depth;

forming a first strip extending in a generally longitudinal direction in the hardened outer metallic layer, the first strip having a second hardness level different from the first hardness level;

forming a second strip in the hardened outer metallic layer having the second hardness level, the first strip and the second strip spaced apart from each other over a longitudinal region;

sensing an angular difference between a first magnetic field associated with the first strip and a second magnetic field associated with the second strip; and

referencing an established relationship between a position of the shaft and the angular difference between the magnetic fields associated with the first strip and the second strip to detect a position of the shaft with respect to a reference point.

2. The method according to claim 1 wherein the first hardness level is greater than the second hardness level.

3. The method according to claim 1 wherein the first hardness level is less than the second hardness level.

4. The method according to claim 1 wherein the first strip comprises a curved segment, and wherein the second strip comprises a generally linear segment spaced apart from the curved segment.

5. The method according to claim 1 wherein the first strip and the second strip comprise generally linear segments, wherein the second strip is generally parallel to a rotational axis of the shaft and wherein the first strip is slanted with respect to the second strip.

6. The method according to claim 1 wherein the first strip and the second strip comprise a first generally sinusoidal wave and a second generally sinusoidal wave, wherein the wave are offset in frequency with respect to one another and cross one another at one or more nodes.

7. The method according to claim 1 further comprising storing the established relationship as angular differences and corresponding axial positions of the shaft.

8. The method according to claim 1 further comprising storing the established relationship as magnetic field patterns and corresponding axial positions of the shaft.

9. A system for detecting a position of a shaft, the system comprising:

a shaft comprising a hardened outer metallic layer having a first hardness level with a generally uniform radial depth;

a first strip extending in a generally longitudinal direction in the hardened outer metallic layer, the first strip having a second hardness level different from the first hardness level;

a second strip in the hardened outer metallic layer having the second hardness level, the first strip and the second strip spaced apart from each other over a longitudinal region;

a sensor assembly for sensing an angular difference between a first magnetic field associated with the first strip and a second magnetic field associated with the second strip; and

a data processor for referencing an established relationship between a position of the shaft and the angular difference between the magnetic fields associated with the first strip and the second strip to detect a position of the shaft with respect to a reference point.

10. The system according to claim 9 wherein the first hardness level is greater than the second hardness level.

11. The system according to claim 9 wherein the first hardness level is less than the second hardness level.

12. The system according to claim 9 wherein the first strip comprises a curved segment, and wherein the second strip comprises a generally linear segment spaced apart from the curved segment.

13. The system according to claim 9 wherein the first strip and the second strip comprise generally linear segments, wherein the second strip is generally parallel to a rotational axis of the shaft and wherein the first strip is slanted with respect to the second strip.

14. The system according to claim 9 wherein the first strip and the second strip comprise a first generally sinusoidal wave and a second generally sinusoidal save, wherein the wave are offset in frequency with respect to one another and cross one another at one or more nodes.

15. The system according to claim 9 wherein the sensor assembly comprises a group of magnetoresistive sensors radially aligned with respect to the shaft.

16. The system according to claim 9 further comprising a data storage device for storing the established relationship as angular differences and corresponding axial positions of the shaft.

17. The system according to claim 9 further comprising a data storage device for storing the established relationship as magnetic field patterns and corresponding axial positions of the shaft.