Method for adjusting ferrous article proximity detector

• US 5,818,222 A
• Filed: 06/07/1995
• Issued: 10/06/1998
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Cherry Corporation (ZF Electronics Corp.)
• Inventors: Ramsden, Edward A.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US08/473,225
• Time in Patent Office: 1,217 Days
• Field of Search: 324/202, 324/207.12, 324/207.2, 324/251, 338/32 H, 327/510, 327/511
• US Class Current: 324/202
• CPC Class Codes: H03K 17/9517 using galvanomagnetic devices

Abstract

An improved proximity detector comprising a hall effect sensor affixed to a permanent magnet, where the improvement comprises tuning the operational gradient of the magnetic field normal to the face of the detector. An apparatus and method for tuning the operational gradient of the magnetic field normal to the face of the detector is also discloses and utilizes means for generating magnetic fields parallel and perpendicular to the face of the magnetic proximity detector. The tuning apparatus changes the gradient through the application of magnetic tuning fields to the sensor magnetic, thereby changing the operational gradient axis, the operational gradient strength or both.

Claims

1. A method of adjusting a magnetic proximity detector incorporating a magnet, the magnetic proximity detector being responsive to an externally induced magnetic field gradient normal to a face of the magnetic proximity detector, comprising the steps of:

measuring an operational gradient of a magnetic field normal to said face of said magnetic proximity detector;

determining a modification field that, when applied to said magnetic proximity detector, will adjust a magnetic field axis of said magnet in a predetermined manner;

applying said modification field to said magnetic proximity detector; and

removing said modification field from said magnetic proximity detector,

whereby said adjusted magnet effects said operational gradient of said magnetic proximity detector.

2. The method of claim 1 wherein the step of measuring an operational gradient of a magnetic field normal to a face of said magnetic proximity detector further comprises the steps of:

applying a sequence of magnetic fields having predetermined gradients to said face of said magnetic proximity detector until a first of said sequence causes an activation of said magnetic proximity detector.

3. The method of claim 2 wherein said sequence of magnetic fields having predetermined gradients comprises a set of magnetic fields having gradients which increase linearly.

4. The method of claim 2 wherein said series of magnetic fields having predetermined gradients comprises a set of magnetic fields having gradients which increase exponentially.

5. The method of claim 2 wherein the step of determining a modification field comprises the steps of:

indexing into a table of predetermined modification values with said first of said sequence of magnetic fields; and

retrieving a predetermined modification value associated with said first of said sequence of magnetic field.

6. The method of claim 1 wherein said modification field is substantially parallel to said face of said magnetic proximity detector.

7. The method of claim 1 wherein said modification field is substantially perpendicular to said face of said magnetic proximity detector.

8. The method of claim 1 wherein said modification field is both parallel and perpendicular to said face of said magnetic proximity detector.

9. An apparatus for adjusting the magnetic field of a magnetic proximity detector responsive to an externally induced magnetic field gradient normal to a face of the magnetic proximity detector comprising:

a fixture for securing said magnetic proximity detector, said fixture having an axis substantially perpendicular to a face of said magnetic proximity detector;

actuating means for actuating said magnetic proximity detector, said actuating means mounted in said fixture and having an axis substantially perpendicular to said face of said magnetic proximity detector;

first means for generating a first magnetic field, said first means being arranged relative to said fixture and oriented such that said first magnetic field is substantially perpendicular to said axis; and

second means for generating a second magnetic field, said second means being arranged relative to said fixture and oriented such that said second magnetic field is substantially parallel to said axis.

10. The apparatus of claim 9 wherein said first means for generating said first magnetic field comprises at least one coil having a magnetic field axis substantially parallel to said axis.

11. The apparatus of claim 9 wherein said second means for generating said second magnetic field comprises at least one coil having a magnetic field axis substantially perpendicular to said axis.

12. The apparatus of claim 9 further comprising:

computation means adapted to control said first generating means and said second generating means.

13. The apparatus of claim 9 further comprising:

means for measuring the operational gradient of a magnetic field normal to said face of said magnetic proximity detector.

14. The apparatus of claim 12 wherein said computation means is further adapted to control said first generating means and said second generating means based upon said measured operation gradient.

15. In a magnetic proximity detector incorporating a magnet, the magnetic proximity detector being responsive to an externally induced magnetic field gradient normal to a face of the magnetic proximity detector, the improvement comprising adjusting an operational gradient of a magnetic field normal to said face of said magnetic proximity detector in a magnetic field that alters a magnetic field axis of said magnet in a predetermined manner, said magnetic field being applied to said magnetic proximity detector for a predetermined period of time, whereby said altered magnet effects said operational gradient of said magnetic proximity detector.

16. An improved magnetic proximity detector incorporating magnet, the magnetic proximity detector being responsive to an externally induced magnetic field gradient normal to a face of the magnetic proximity detector, produced by a method comprising the steps of:

measuring an operational gradient of a magnetic field normal to a face of said magnetic proximity detector;

determining a modification field that, when applied for a predetermined period of time to said magnetic proximity detector, will adjust a magnetic field axis of said magnet in a predetermined manner; and

applying said modification field to said magnetic proximity detector for said predetermined period of time,

whereby said adjusted magnet effects said operational gradient of said magnetic proximity detector.

17. The method of claim 16 wherein the step of measuring an operational gradient of a magnetic field normal to a face of said magnetic proximity detector further comprises the steps of:

applying a sequence of magnetic fields having predetermined gradients to said face of said magnetic proximity detector until a first of said sequence causes an activation of said magnetic proximity detector.

18. The method of claim 17 wherein said sequence of magnetic fields having predetermined gradients comprises a set of magnetic fields having gradients which increase linearly.

19. The method of claim 17 wherein said series of magnetic fields having predetermined gradients comprises a set of magnetic fields having gradients which increase exponentially.

20. The method of claim 17 wherein the step of determining a modification field comprises the steps of:

indexing into a table of predetermined modification values with said first of said sequence of magnetic fields; and

retrieving a predetermined modification value associated with said first of said sequence of magnetic field.