Method and apparatus for determining thickness of a lubricant film

• US 7,066,027 B2
• Filed: 08/24/2001
• Issued: 06/27/2006
• Est. Priority Date: 08/29/2000
• Status: Expired due to Fees

• Current Assignee: UNDIVIDED ONE HALF INTEREST TO: THE UNIVERSITY OF SHEFFIELD AND THE UNIVERSITY OF BRISTOL, University of Bristol
• Original Assignee: University of Bristol, University of Sheffield
• Inventors: Drinkwater, Bruce Walton, Dwyer-Joyce, Robert Sean, Donohoe, Cornelius Joseph
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): SAINT SURIN, JACQUES M
• Application Number:
  US10/362,813
• Publication Number:
  US 20040045356A1
• Time in Patent Office: 1,768 Days
• Field of Search: 735/79, 735/97, 736/02, 735/93, 736/59, 736/60, 736/15, 736/44, 736/65, 736/27, 736/29
• US Class Current: 73/579
• CPC Class Codes: F16C 19/52 with devices affected by abnormal or undesired conditions
• CPC Class Codes: F16C 33/6648 in a porous or resinous body, e.g. a cage impregnated with the liquid
• CPC Class Codes: F16C 33/6651 in recesses or cavities provided in retainers, races or rolling elements
• CPC Class Codes: F16C 33/667 related to conditioning, e.g. cooling, filtering
• CPC Class Codes: F16C 33/6674 related to the amount supplied, e.g. gaps to restrict flow of the liquid
• CPC Class Codes: F16N 29/00 Special means in lubricating arrangements or systems providing for the indication or detection of undesired conditions; Use of devices responsive to conditions in lubricating arrangements or systems
• CPC Class Codes: G01B 17/025 for measuring thickness of coating
• CPC Class Codes: G01M 13/04 Bearings
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0226 Oils, e.g. engine oils
• CPC Class Codes: G01N 2291/02854 Length, thickness
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14

Abstract

A method and apparatus of determining the thickness of a lubricant film disposed between two bodies by measuring and performing a frequency spectrum analysis on a reflected or transmitted part of an ultrasound wave propagated towards said film is disclosed.

Claims

1. A method of determining the thickness of a film disposed between two bodies in a two body interface assembly, the method comprising propagating an ultrasound wave towards the film;

measuring a reflection coefficient from a reflection of said ultrasound wave at an interface including said film, said reflection coefficient being indicative of a proportion of the ultrasound wave which is reflected at said interface; and

determining the thickness by quantifying the stiffness of the film from said reflection coefficient in conjunction with at least one of the group consisting of;

a spring model of said assembly and continuum model of said assembly.

2. The method as claimed in claim 1 wherein the ultrasound wave is propagated through the first of said two bodies substantially normal to an interface between said film and said first body (“

the first interface”

).

3. The method as claimed in claim 2 further comprising the step of detecting the proportion of the ultrasound wave which is reflected at said interface.

4. The method as claimed in claim 1 further comprising the step of detecting the proportion of the ultrasound wave which is reflected at the interface between the second of said two bodies and the film (“

the second interface”

).

5. The method as claimed in claim 1 further comprising the step of detecting the proportion of the ultrasound wave which is transmitted through said two bodies and said film.

6. The method as claimed in claim 1 wherein a single transducer is used both to generate the ultrasound wave and detect the reflection thereof.

7. The method as claimed in claim 1 wherein the ultrasound wave is propagated through a coupling medium towards said first body.

8. The method as claimed in claim 7 wherein said coupling medium comprises water.

9. The method as claimed in claim 1 including the step of determining film thickness from the shape and gradients contained within a whole measurable reflection frequency spectrum.

11. The method as claimed in claim 1 wherein said two bodies are parts of a lubricated bearing such as a journal bearing, roller element bearing, piston-ring liner, cam-tappet, wet seal, thrust pad bearing or gear teeth.

12. The method as claimed in claim 1 further comprising measuring and performing a frequency spectrum analysis on said reflection of said ultrasound wave.

13. The method as claimed in claim 12 wherein the film thickness is determined from the shape and gradients of the frequency spectrum over a frequency range below the resonant frequency of the film.

14. The method as claimed in claim 1 wherein said film is a lubricant film.

15. The method as claimed in claim 1 wherein said film has a thickness less than 10 microns.

10. The method as claimed in 1 further including the step of determining film thickness from a region where the reflection coefficient is linearly proportional to frequency.

16. An apparatus for determining the thickness of a lubricant film comprising:

means for generating an ultrasound wave and propagating same towards a film whose thickness it is desired to determine;

a detector for detecting a reflection coefficient from a reflected part of said ultrasound wave which has been reflected at an interface including said film, said reflection coefficient being indicative of a proportion of the ultrasound wave which is reflected at said interface; and

a processor for determining the thickness of the film by quantifying the stiffness of the film from said reflection coefficient in conjunction with at least one of the group consisting of;

a spring model and continuum model.