Method and apparatus for on-sine monitoring of wear in machinery

• US 4,841,244 A
• Filed: 09/18/1986
• Issued: 06/20/1989
• Est. Priority Date: 10/11/1985
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Chambers, Keith W.
• Primary Examiner(s): Strecker, Gerard R.
• Assistant Examiner(s): EDMONDS, WARREN
• Application Number:
  US06/908,731
• Time in Patent Office: 1,006 Days
• Field of Search: 324/204, 324/227, 324/236, 324/262, 324/445, 324/71.1, 324/71.4, 73/861.05, 73/861.11, 340/631, 340/64
• US Class Current: 324/204
• CPC Class Codes: G01N 15/0656 using electric, e.g. electrostatic methods or magnetic methods by investigating individual particles G01N15/1031, G01N15/12
• CPC Class Codes: G01N 27/72 by investigating magnetic variables
• CPC Class Codes: G01N 33/2858 metal particles

Abstract

A detector for producing an electrical signal proportional to the concentration of ferromagnetic particulate material in a fluid stream includes a sensing coil arranged to form the inductance coil of a radio frequency oscillator arranged to produce an electrical signal at a base frequency, a magnetic trap for producing a magnetic field and a support for supporting the sensing coil and the magnetic trap in juxtaposition to one another such that, when the coil is disposed within or proximate the fluid stream and electrically connected to the oscillator, energization of the magnetic trap causes ferromagnetic particulate material proximate the coil to be attracted toward the coil resulting in a deviation of the frequency of the signal from the base frequency proportional to the concentration of ferromagnetic particulate material in the fluid stream. The detector has particular utility in monitoring wear in machines employing a lubricating fluid for lubricating ferromagnetic components which produce ferromagnetic particulate wear debris during operation.

Claims

1. A device for producing an electrical signal which is proportional to the concentration of ferromagnetic particulate material in a fluid stream, said device comprising, in combination:

a sensing coil arranged to form the inductance coil of and connected to a radio frequency oscillator arranged to produce an electrical signal at a base frequency;

magnetic trap means for producing a magnetic field; and

support means for supporting said sensing coil and said magnetic trap measn in juxtaposition to one another such that, when said coil is disposed within or proximate said fluid stream and electrically connected to radio frequency oscillator, energization of said magnetic trap measn causes ferromagnetic particulate material proximate said coil to be attracted toward said coil resulting in a deviation of the frequency of said signal from said base frequency proportional to the concentration of ferromagnetic particulate material in said fluid stream.

2. A device as defined in claim 1, wherein the base frequency of said oscillator is about 34 MHz.

3. A device as defined in claim 1, wherein said trap is an electromagnet coaxially disposed about said coil.

4. A device as defined in claim 1, wherein said trap is an electromagnet coaxially disposed within said coil.

5. A device as defined in claim 1, wherein said support means includes non-magnetic, electrical insulating means connecting said coil and said magnetic trap means.

6. A device as defined in claim 5, wherein said insulating means is an epoxy matrix.

7. A device as defined in claim 1, wherein said trap means is adapted to be selectively energized and de-energized.

8. A device for producing an electrical signal which is proportional to the concentration of ferromagnetic particulate material in a fluid, said device comprising, in combination:

a housing having a fluid passage extending therethrough;

a radio frequency oscillator for producing an electrical signal at a predetermined base frequency, said oscillator having an inductance coil disposed in said housing in coaxial relation with respect to said passage;

magnetic trap means disposed in said housing in electrically insulated relation with respect to said inductance coil, said magnetic trap means being arranged to produce a magnetic field about said inductance coil such that energization of said magnetic trap means causes ferromagnetic particulate material in said passage and proximate said coil to be attracted toward said coil and results in a deviation of the frequency of said signal from said base frequency proportional to the concentration of ferromagnetic particulate material in said fluid stream.

9. A device as defined in claim 8, said inductance coil forming in part a surface of said passage whereby trapped ferromagnetic particulate material is magnetically urged aganist said surface.

10. A device as defined in claim 8, further including means for selectively energized and de-energizing said magnetic trap means.

11. A device as defined in claim 8, said magnetic trap means being electromagnet disposed in said housing concentrially about inductance coil.

12. A device as defined in claim 8, further including means for determining the magnitude of said deviation and a quantity linearly related to the concentration of ferromagnetic particulate material in fluid passing through said passage.

14. A device as defined in claim 12, said means including a microprocessor.

15. A device as defined in claim 8, wherein the base frequency of said oscillator is about 34 MHz.

13. A device as defined in calim 12, said quantity being the ratio of the magnitude of said deviation to the duration of said deviation.

16. An apparatus for monitoring to rate if wear of a machine emeploying a lubricating fluid for lubricating ferromagnetic components which produce ferromagnetic particulate wear debris during operation, said apparatus comprising, in combination:

a detector for producing an electrical signal proportional to the concentration of ferromagnetic particulate material in said fluid, said detector including a housing a fluid passage extending therethrough a radio frequency oscillator for producing an electrical signal at a predetermined base frequency, said oscillator having an inductance coil disposed in said housing in coaxial relation with respect to said passage, magnetic trap means disposed in said housing in electrically insulates relation with respect to said inductance coil, said magnetic trap means being arranged to produce a magnetic field about said inductance coil such that energization of said magnetic trap means causes ferromagnetic particualte material in said passage and proximate said coil to be attracted toward said coil and results in a deviation of the frequency of said signal from said base frequency proportional to the concentration of ferromagnetic particulate material in said fluid stream;

control means for energizing and de-energizing said magnetic trap means at predetermined timed intervals;

means for determining, at the end of each said predetermined timed interval, a quantity linearly related to the concentration of ferromagnetic partoculate material in fluid passed through said detector, determining the rate of change of said quantities and activating an alarm means when the rate of change of said quantity exceeds a predetermined threshold value.

17. A device as defined in claim 16, further including timing means for determining a time interval within which said magnetic trapping means is energized.

18. A device as defined in claim 17, further including counter means for counting the number of cycles of said output signal during said time interval and means responsive to a predetermined count for de-activating said timing means and thereafter de-energizing said magnetic trap means.

19. A device as defined in claim 18, further including means for activating said timing means at a predetermined time interval after energizing said magnetic trap means.

20. A device as defined in claim 16, said responsive means including timing means, counter means and microprocessor means, said microprocessor means being adapted to signal said control means whereby to energize said magnetic trap means at equal predetermined timed intervals, activate said timing means and said counter means at a predetermined time interval after energizing said trap means, deactivate said timing means and counter means when the count of said counter means attains a predetermined value, and thereafter de-activate said trap means, and determine a quantity related to the concentration of the ferromagnetic particulate material in said lubrication fluid.

21. A method of determining a quantity related to the concentratoin of ferromagnetic material in a fluid, comprising the steps of:

(a) passing a sample of said fluid through a fluid conduit;

(b) electromagnetically trapping ferromagnetic particulate material at a predetermined site in said fluid conduit at which an inductance coil of a radio frequency oscillator is coaxially disposed;

(c) determining the deviation, during said electromagnetically trapping step, of the frequency of the output signal of said oscillator from a reference signal; and

(d) determining the ratio of said deviation to the duration of said deviation, said ratio being linearly proportional to the concentration of said ferromagnetic particulate material in said fluid.

22. A method as defined in claim 21, wherein said step of determining said deviation including determining the change in frequency of said signal during said electromagnetically trapping step for a predetermined, fixed trapping interval.

23. A method as defined in claim 21, wherein said step of determining said deviation including determining the trapping interval within which the frequency of said signals attains a predetermined value.

24. A method as defined in claim 21, wherein said step of determining said deviation including determining the number of cycles of the frequency of said signal which occur within a fixed, predetermined trapping interval.

25. A method as defined in claim 21, wherein said step of determining said deviation including determining the trapping interval within which the number of cycles of the frequency of said signal reaches a predetermined value.

26. A method of determining the degree of wear of a machine having ferromagnetic components subjected to wear during operation resulting in the production of frerromagnetic particulate material, said machine having a lubrication system utilizing a lubrication fluid, in which said ferromagnetic particulate material becomes entrained, for lubricating said components, said method comprising the steps of:

(a) determining, at predetermined intervals of time, a quantity related to the concentration of ferromagnetic particulate material in said fluid in accordance with the method of claim 22;

(b) determining the rate of change of said quantity, a substantially constant rate of change of concentration being indicative of nornal wear and a non-linear, increasing rate of change of concentration being indicative of excessive wear of said machine.

27. A method of determining the degree of wear of a machine having ferromagnetic components subjected to wear during operation resulting in the production of feromagnetic particulate material, said machine having a lubrication system utilizing a lubrication fluid, in which said ferromagnetic particulate material becomes entrained, for lubricating said components, said method comprising the steps of:

(a) determining, at pedetermined intervals of time, a quantity related to the concentration of ferromagnetic particulate material in said fluid in accordance with the method of claim 22;

(b) determining the rate of change of said quantity, a substantially constant rate of change of concentration being indicative of normal wear and a non-linear, increasing rate of change of concentration being indicative of excessive wear of said machine.

28. A method of determining the degree of wear of a machine having ferromagnetic components subjected to wear during operation resulting in the production of ferromagnetic particulate material, said machine having a lubrication system utilizing a lubrication fluid, in which said ferromagnetic particulate material becomes entrained, for lubricating said components, said method comprising the steps of:

(a) passing a sample of said fluid through a fluid conduit having (i) an electromagnet concentrically disposed thereabout at a predetermined site thereof and (ii) an inductance coil of an oscillator circuit coaxially disposed with respect to said conduit at said site;

(b) energizing said electromagnet to trap ferromagnetic particulate material at said site;

(c) activating a timing means to determine a trapping interval;

(d) counting the number of cycles of the signal of said oscillator circuit which occur within said trapping interval;

(e) deactivating said timing means when said count reaches a predetermined value;

(f) de-energizing said electromagnet;

(g) determining the ratio of said count to said trapping interval;

(h) repeating steps (a) to (e) at fixed predetermined time intervals; and

(i) determining the rate of change of said ratio and activating an alarm means if said rate of change exceeds a predetermined threshold level.

29. A method of determining the effective means particle size of ferromagnetic wear debris in a lubricating fluid, comprising the steps of:

(a) passing a sample of said fluid through a fluid conduit having an electromagnet associated therewith for trapping within said conduit ferromagnetic wear debris in said fluid and a detector for producing an output signal proportional to the concentration of ferromagnetic wear debris in said lubricating fluid at said trapping site;

(b) determining the value of the current passing through said electromagnet at which the output of said detector is zero;

(c) converting said value of said current to a number indicative of the mean particle size of said ferromagnetic wear debris.

30. A method as defined in claim 29, wherein step (b) includes the step of adjusting the magnitude of the electrical current applied to said electromagnet until the output of said detector is zero.

31. A method as defined in claim 29, wherein step (c) incudes the step of multiplying said value of said current by a predetermined proportionality constant to produce said number.

32. A method as defined in claim 29, wherein step (b) includes the step of adjusting the magnitude of the electrical current applied to said electromagnet until the output of set detector is zero;

and wherein step (c) includes the step of multiplying said value of said current by a predetermined proportionality constant to produce said number.