Systems for recording position information in a magnetic layer on a piston rod

• US 7,307,418 B2
• Filed: 04/24/2006
• Issued: 12/11/2007
• Est. Priority Date: 05/06/2003
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Low, Thomas P., Clark, C. Bruce, Pelrine, Ronald E., Eckerle, Joseph S., Smith, Chris
• Primary Examiner(s): LEDYNH, BOT L
• Application Number:
  US11/409,576
• Publication Number:
  US 20060192552A1
• Time in Patent Office: 596 Days
• Field of Search: 324210-213, 32420724-20726, 735/143.1, 735/143.9
• US Class Current: 324/210
• 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: F16F 9/3221 of piston rods
• CPC Class Codes: F16F 9/3292 Sensor arrangements
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G11B 5/656 containing Co containing inorganic, non-oxide compounds of Si, N, P, B, H or C G11B5/657; containing oxygen G11B5/658
• CPC Class Codes: G11B 5/667 including a soft magnetic layer
• CPC Class Codes: G11B 5/7368 Non-polymeric layer under the lowermost magnetic recording layer base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: H01F 10/16 containing cobalt H01F10/126 , H01F10/13 take precedence

Abstract

Described are system for recording piston rod position information in a magnetic layer on the piston rod. A piston rod has a magnetically hard layer formed thereon to provide a recording medium. A magnetic pattern is recorded in the magnetically hard layer. A magnetic field sensor disposed adjacent to the piston rod senses the recorded magnetic pattern while the piston rod is moving and generates signals in response to the magnetic pattern that are used to determine a position of the piston rod.

Claims

1. A piston rod position sensing system, comprising:

a ferromagnetic steel piston rod;

a magnetically hard layer formed on the ferromagnetic steel piston rod to provide a recording medium, a magnetic pattern being recorded in the magnetically hard layer, wherein the magnetic pattern includes a first magnetized line extending parallel to an axis of the piston rod and a second magnetized line extending along a length of the piston rod and diverging away from the first magnetized line; and

a magnetic field sensor disposed adjacent to the piston rod to sense the magnetic pattern recorded in the magnetically hard layer while the piston rod is moving and to generate signals, in response to the sensed magnetic pattern, that are used to determine a position of the piston rod.

2. The piston rod position sensing system of claim 1, further comprising a magnetically soft layer disposed between the magnetically hard layer and the piston rod.

3. The piston rod position sensing system of claim 1, further comprising a non-magnetic layer disposed between the magnetically hard layer and the piston rod.

4. The piston rod position sensing system of claim 1, further comprising a protective layer disposed on the magnetically hard layer.

5. The piston rod position sensing system of claim 1, wherein an area bounded by the first and second magnetized lines is magnetized.

6. The piston rod position sensing system of claim 1, further comprising circuitry for computing one of a velocity and a direction of motion of the piston rod from readings of the magnetic pattern.

7. A piston comprising:

a ferromagnetic steel piston rod extending axially from the piston; and

a magnetically hard layer formed on the ferromagnetic steel piston rod to provide a recording medium for magnetically storing bits of information along a length of the piston rod, a magnetic pattern being recorded in the magnetically hard layer, wherein the magnetic pattern includes a first magnetized line extending parallel to an axis of the piston rod and a second magnetized line extending helically along a length of the piston rod.

8. The piston of claim 7, wherein an area between the first and second magnetized lines is magnetized.

9. The piston of claim 7, further comprising a magnetically soft layer disposed between the magnetically hard layer and a magnetic substrate of the rod.

10. The piston of claim 7, further comprising a non-magnetic layer disposed between the magnetically hard layer and a surface of the piston rod.

11. The piston of claim 7, further comprising a protective layer disposed on the magnetically hard layer.

12. A piston rod position sensing system, comprising:

a cylinder;

a piston arranged within the cylinder for movement therein, the piston having a ferromagnetic steel piston rod extending axially from the piston;

a magnetically hard layer formed on the ferromagnetic steel piston rod to provide a recording medium, a magnetic pattern being recorded in the magnetically hard layer, wherein the magnetic pattern includes a first magnetized line extending parallel to an axis of the piston rod and a second magnetized line extending along a length of the piston rod and diverging away from the first magnetized line; and

a plurality of magnetic field sensors disposed adjacent to the piston rod, each magnetic field sensor sensing a portion of the recorded magnetic pattern while the piston rod is moving relative to the cylinder and generating signals, in response to the sensed portion of the magnetic pattern, for use in determining a position of the piston rod.

13. The piston rod position sensing system of claim 12, further comprising a magnetically soft layer disposed between the magnetically hard layer and the piston rod.

14. The piston rod position sensing system of claim 12, further comprising a non-magnetic layer disposed between the magnetically hard layer and the piston rod.

15. The piston rod position sensing system of claim 12, further comprising a protective layer disposed on the magnetically hard layer.

16. The piston rod position sensing system of claim 12, wherein an area bounded by the first and second magnetized lines is magnetized.

17. The piston rod position sensing system of claim 12, further comprising circuitry for computing one of a velocity and a direction of motion of the piston rod from readings of the magnetic pattern.

18. A piston rod position sensing system, comprising:

a ferromagnetic steel piston rod; and

magnetically hard layer formed directly on an outer surface of the ferromagnetic steel piston rod to provide a recording medium in which a magnetic pattern is recorded longitudinally, wherein the magnetic pattern includes a first magnetized line extending parallel to an axis of the piston rod and a second magnetized line extending along a length of the piston rod and diverging away from the first magnetized line.