Method and apparatus for determining thickness of a lubricant film

• US 20040045356A1
• Filed: 08/25/2003
• Published: 03/11/2004
• Est. Priority Date: 08/29/2000
• Status: Active Grant

• Current Assignee: UNDIVIDED ONE HALF INTEREST TO: THE UNIVERSITY OF SHEFFIELD AND THE UNIVERSITY OF BRISTOL, University of Bristol
• Original Assignee: UNDIVIDED ONE HALF INTEREST TO: THE UNIVERSITY OF SHEFFIELD AND THE UNIVERSITY OF BRISTOL, University of Bristol
• Inventors: Drinkwater, Bruce Walton, Dwyer-Joyce, Robert Sean, Donohoe, Cornelius Joseph
• Granted Patent: US 7,066,027 B2
• Time in Patent Office: Days
• 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

Method 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.

Claims

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

2. 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 lubricant film and said first body (“

the first interface”

).

3. 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. Method as claimed in any of the preceding claims 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 lubricant film (“

the second interface”

).

5. Method as claimed in any of preceding claims further comprising the step of detecting the proportion of the ultrasound wave which is transmitted through said two bodies and lubricant film.

6. Method as claimed in any of the preceding claims wherein a single transducer is used both to generate the ultrasound wave and detect the reflection thereof.

7. Method as claimed in any of the preceding claims wherein the ultrasound wave is propagated through a coupling medium towards said first body.

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

9. Method as claimed in any of claims 1-8 including the step of determining film thickness from the shape and gradients contained within the whole measurable reflection frequency spectrum.

10. Method as claimed in claim 9 including the step of determining transmitted frequencies due to resonance.

11. Method as claimed in claim 10 further including the step of determining film thickness from the region where the reflection coefficient is linearly proportional to frequency.

12. Method as claimed in any of claims 1-8 wherein the thickness of the lubricant film is determined by computing the stiffness of the liquid layer from a spring model analysis of the reflected or transmitted signal.

13. Method as claimed in any of claims 1-8 wherein the thickness of the lubricant film is determined using a continuum model analysis of the reflected or transmitted signal.

14. Method as claimed in any of claims 1-8 wherein the thickness of the lubricant film is determined by quantifying the attenuation of a shear ultrasound wave in the lubricant film.

15. Method as claimed in any of the preceding claims 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.

17. Apparatus for performing the method of any of the preceding claims comprising means for generating an ultrasound wave and propagating same towards a lubricant film whose thickness it is desired to determine;

a detector for detecting a reflected or transmitted part of said ultrasound wave;

a processor for determining the thickness of the lubricant film by performing a frequency spectrum analysis on the reflected or transmitted part of said ultrasound wave.

16. Method of determining the thickness of a lubricant film substantially as described herein with reference to any appropriate combination of the accompanying drawings.

18. Apparatus for determining the thickness of a lubricant film disposed between two bodies substantially as described herein with reference to any appropriate combination of the accompanying drawings.