Position sensing apparatus

• US 6,690,160 B2
• Filed: 04/22/2002
• Issued: 02/10/2004
• Est. Priority Date: 04/22/2002
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Gray, Keith Wayland, Wright, Walter Craig, Killen, Dale
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): KINDER, DARRELL D
• Application Number:
  US10/127,785
• Publication Number:
  US 20030197504A1
• Time in Patent Office: 659 Days
• Field of Search: 324/207.13, 324/207.2, 324/207.21, 324/207.24, 324/232
• US Class Current: 324/207.24
• CPC Class Codes: F15B 15/2861 using magnetic means
• CPC Class Codes: G01D 5/04 using levers; using cams; using gearing

Abstract

A cylinder position sensing system includes a cylinder housing which slidably receives a rod or shaft element. The cylinder housing has an end piece which slidably receives the shaft element. A first axial groove is formed in the shaft element, and a first magnet member is mounted in the first groove. A second helical groove is formed in the shaft element and is spaced apart from the first groove. A second magnet member is mounted in the second groove. A magnetic field sensor is mounted in the cylinder housing so that the sensor generates an output signal as a function of a relative distance between the first and second magnet members as the second element moves with respect to the first element. Preferably, the shaft element includes a central cylindrical shaft and a hollow cylindrical sleeve mounted over and receiving the shaft. Preferably, the first and second grooves are formed in an inner surface of the sleeve, and the sleeve and the end piece are formed of nonferrous material.

Claims

1. A position sensing system comprising:

a first element;

a second element slidable with respect to the first element;

a first groove in the second element, the first groove extending parallel to a central axis of the second element;

a first magnet member mounted in the first groove;

a second groove in the second element, the second groove being helical and being spaced apart from the first groove;

a second magnet member mounted in the second groove; and

a magnetic field sensor mounted in the first element, the sensor generating an output signal as a function of a relative distance between the first and second magnet members as the second element moves with respect to the first element.

2. The position sensing system of claim 1, wherein the second element comprises:

a cylindrical shaft; and

a hollow cylindrical sleeve mounted over and receiving the shaft, the first and second grooves being formed in an inner surface of the sleeve.

3. The position sensing system of claim 1, wherein:

the second element comprises a cylindrical shaft, and a hollow cylindrical sleeve mounted over and receiving the shaft; and

the first element comprises a hollow cylindrical housing having an end piece with a shaft bore extending therethrough, a wall of the bore slidably engaging the sleeve.

4. The position sensing system of claim 3, wherein:

the sleeve and the end piece are formed of non-ferrous material.

5. The position sensing system of claim 3, wherein:

an annular sensor groove is formed in a surface of the shaft bore, the magnetic field sensor being mounted in the sensor groove.

6. The position sensing system of claim 5, wherein:

first and second seal grooves are formed in the surface of the shaft bore on opposite sides of the sensor groove;

a high pressure seal element is mounted in the first seal groove and sealingly and slidably engages an outer surface of the sleeve; and

a wiper seal element is mounted in the second seal groove and sealingly and slidably engages an outer surface of the sleeve.

7. The position sensing system of claim 2, wherein:

the sleeve is formed of non-ferrous material.

8. A position sensing system comprising:

a hollow cylindrical housing element;

a shaft element slidably received by the housing element, the shaft element comprising a central shaft and a hollow cylindrical sleeve mounted on the shaft;

a first groove in the sleeve, the first groove extending parallel to a central axis of the shaft;

a first magnet member mounted in the first groove;

a second groove in the sleeve, the second groove being helical and being spaced apart from the first groove;

a second magnet member mounted in the second groove; and

a magnetic field sensor mounted in the housing element, the sensor generating an output signal as a function of a relative distance between the first and second magnet members as the shaft moves with respect to the housing element.

9. The position sensing system of claim 8, wherein:

the first and second grooves are formed in an inner surface of the sleeve.

10. The position sensing system of claim 8, wherein:

the housing element comprises an end piece with a shaft bore extending therethrough, a wall of the bore slidably engaging the sleeve.

11. The position sensing system of claim 10, wherein:

the sleeve and the end piece are formed of non-ferrous material.

12. The position sensing system of claim 10, wherein:

an annular sensor groove is formed in a surface of the shaft bore, the magnetic field sensor being mounted in the sensor groove.

13. The position sensing system of claim 12, wherein:

first and second seal grooves are formed in the surface of the shaft bore on opposite sides of the sensor groove;

a high pressure seal element is mounted in the first seal groove and sealingly and slidably engages an outer surface of the sleeve; and

a wiper seal element is mounted in the second seal groove and sealingly and slidably engages an outer surface of the sleeve.

14. The position sensing system of claim 9, wherein:

the sleeve is formed of non-ferrous material.

15. A position sensing system comprising:

a first element;

a second element having an axial length and being movable with respect to the first element;

a first magnet member mounted on the second element, the first magnet member extends parallel to a central axis of the second element;

a second magnet member mounted on the second element, the second magnet member being helical and spaced apart from the first magnet member, and a spacing between the magnet members varying as a function of an axial position along the second member; and

a magnetic field sensor supported by the first element, the sensor generating an output signal as a function of the spacing between the first and second magnet members as the second element moves with respect to the first element.

16. The position sensing system of claim 15, wherein:

a first groove is formed in the second element, the first groove extending parallel to a central axis of the second element, the first magnet member being mounted in the first groove;

a second groove is formed in the second element, the second groove being helical and being spaced apart from the first groove, the second magnet member being mounted in the second groove.