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1. (WO2009138106) PRÉDICTION D'INTERVALLE DE RELUBRIFICATION
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

14 May 2008

CLAIMS

1. A method of predicting when a grease in a grease-lubricated rolling element bearing will reach an unacceptable condition, the method comprising the steps of: running the grease-lubricated bearing; - measuring a parameter that is directly or indirectly indicative of a degree of breakdown of a lubricant film separating the rolling contacts, where the measurement values are recorded at specific intervals over a predefined measurement period, so as to obtain a time series of parameter values; analyzing the time series and constructing a dynamic model that predicts the evolution of parameter values; extrapolating the time series, based on the dynamic model, to predict future values of the time series; determining a time at which a value of the extrapolated time series will exceed a predefined limit, whereby said predefined limit is representative of the unacceptable grease condition.

2. The method according to claim 1 , wherein the time determined from the extrapolated times series serves as a prediction of a relubrication interval of the rolling element bearing.

3. The method according to claim 1 or 2, wherein the step of running the bearing is performed at substantially constant load and speed.

4. The method according to any of the preceding claims, wherein the measurement period begins after an initial churning phase of bearing lubrication has ended.

5. The method according to any of the preceding claims, wherein the step of measuring comprises measuring a plurality of parameters indicative of the degree of lubricant film breakdown, such that a time series is obtained for each of the measured parameters; the step of analyzing comprises analyzing each individual time series and constructing a corresponding dynamic model that predicts the evolution of the corresponding time series; the step of extrapolating comprises extrapolating each time series; - the step of determining comprises determining from each extrapolated time series a time at which a predefined limit will be exceeded.

6. The method according to any of the preceding claims, wherein the step of measuring comprises measuring bearing temperature and the predefined limit in the step of determining is a maximum temperature value.

7. The method according to any of the preceding claims, wherein the step of measuring comprises measuring power consumption of a drive means that powers the running of the bearing and the predefined limit in the step of determining is a maximum power consumption value.

8. The method according to any of the preceding claims, wherein the step of measuring comprises measuring a parameter that is directly indicative of the degree of lubricant film breakdown.

9. The method according to claim 8, wherein the measured parameter is a capacitance or an electrical contact resistance of the bearing and the predefined limit in the step of determining is a duration of a minimum capacitance value or a duration of a minimum electrical contact resistance value respectively.

10. The method according to any of the preceding claims, wherein the step of analyzing comprises estimating an embedding dimension, m, and a time delay, T, for each time series.

11. The method according to any of the preceding claims, wherein the step of analyzing further comprises calculating the Lyapunov exponents for each time series.

12. The method according to claim 10 or 11 , wherein the step of constructing a dynamic model comprises constructing an m-dimensional phase space for each time series.

13. The method according to claim 12, wherein the step of constructing a dynamic model further comprises estimating a model function for the dynamics, which model function evolves the reconstructed phase space from one state to a next state.

14. The method according to any of the preceding claims, wherein the step of running the bearing is performed such that any rise in bearing temperature is a self-induced temperature rise.

15. The method according to any of claims 1 to 13, wherein the step of running the bearing is performed under controlled temperature conditions, whereby heating means are employed to maintain bearing temperature at a predefined setpoint.

16. The method according to claim 15, wherein the step of measuring comprises measuring successive durations between automatic deactivation and reactivation of the heating means and the predefined limit in the step of determining is a maximum duration value.

17. A device for predicting when a grease in a grease-lubricated bearing will reach an unacceptable condition, the device being arranged to be coupled to a system comprising at least one grease-lubricated rolling element bearing, wherein the device comprises: - means to measure one or more parameters that are directly or indirectly indicative of a degree of breakdown in a lubricant film formed between rolling elements and raceways of the bearing; processing means arranged to:

record a time series of measurement values for each parameter measured when the grease-lubricated bearing is rotatably driven;

analyze each recorded time series and construct a corresponding dynamic model to predict the evolution of the measured parameter it is based on;

extrapolate each time series, based on the corresponding dynamic model, and determine therefrom a time at which a predefined catastrophic value will be reached;

output each determined time value as a prediction of when the grease will reach an unacceptable condition.

18. The device according to claim 18, wherein the processing means comprises a neural network.

19. A system comprising a device according to claim 18 or 19, wherein the system further comprises heating and control means to maintain bearing temperature at a predefined setpoint.